According to Emanuel Swedenborg, why are there different types of angels? Based on various passages in the Bible, Christian tradition holds that there are many types of angels. 

According to Emanuel Swedenborg, if God did not create angels as a separate race, and humans become angels after they die,


Why are there different types of angels?
What kind of person becomes the highest ranking angel?
Does God decide who should become a seraph, cherub, and so on? How does God make the decision?


For instance, Revelation 10 mentions a giant angel. I wonder who was this angel when he was a human.


  Then I saw another mighty angel coming down from heaven. He was robed
  in a cloud, with a rainbow above his head; his face was like the sun,
  and his legs were like fiery pillars. He was holding a little
  scroll, which lay open in his hand. He planted his right foot on the
  sea and his left foot on the land, and he gave a loud shout like the
  roar of a lion. When he shouted, the voices of the seven thunders
  spoke. (Revelation 10:1-3, NIV. emphasis added)
In line with his (Swedish) Lutheran roots, Emanuel Swedenborg (1688-1772) gave little weight to the Christian traditions that had grown up over the centuries, including traditions about a hierarchy of angels. He considered the Bible itself to be the only valid authority for Christian doctrine throughout Christianity as a whole.

As outlined in the question's linked Wikipedia article on the Christian angelic hierarchy, the idea of hierarchies of angels was originated by various Christian theologians over the centuries, and is based only loosely on the Bible. For example:


Though figures such as seraphim and cherubim do appear in the Bible, they are never identified as angels in the biblical text.
There is no biblical warrant for interpreting "thrones or powers or rulers or authorities" in Colossians 1:16 and elsewhere as referring to angelic beings, ranked or otherwise.
The Greek word commonly translated "archangel" simply means "lead messenger." The Bible never says anything about "archangels" as a separately created race or rank of angels. It merely implies through this term that some angels have higher authority or are more powerful than others, similar to leaders and followers among human beings.


Swedenborg did, however, draw heavily on his (claimed) experiences in the spiritual world over the last twenty-seven years of his life in interpreting what the Bible means when it refers to angels and heavens.

Based on his reading of the Bible and on his spiritual world experiences, Swedenborg stated that although there are higher and lower angels, there are no archangels, and no separate races of angels. Angels are higher or lower in heaven based on how fully they accept God (or Christ) into their lives. This is a function of how thoroughly, fully, and willingly they undergo the process of rebirth, or regeneration, through believing in God and following God's commandments during their lifetimes on earth.

Swedenborg agreed with Paul (2 Corinthians 12:2) in saying that there are three heavens (see Heaven and Hell #29-40). These heavens are:


The central, highest, third, or "heavenly" (traditionally "celestial") heaven
The middle, second, or "spiritual" heaven
The outmost, lowest, first, or "natural" heaven


The angels in the highest heaven are in that heaven because they receive God's love and truth directly into their hearts, or intentions, and act on it immediately and in complete innocence. They do not have to think about it and consider whether or not it is good and true. They trust in the Lord, and in everything that comes from the Lord, simply and completely--and they have a very clear and instantaneous perception of what does and does not come from the Lord. They are therefore the wisest and most powerful angels. However, at a distance they appear like little children because of their full innocence and trust in the Lord. (Compare Jesus' saying in Matthew 18:3: "Truly I tell you, unless you change and become like little children, you will never enter the kingdom of heaven.") These angels are the beating heart of heaven.

The angels in the middle heaven are in that heaven because they receive God's love and truth in a more indirect and intellectual fashion. Before they act on some idea or feeling that enters their mind or heart, they must first think about it, examine it in their minds, research it further, and come to a rational conclusion that it is indeed good and true, and therefore from God, based on what they have learned. They are therefore less innocent and trusting in God, and more intellectual in their approach to life. These angels are the teachers and intellectual leaders of heaven.

The angels in the lowest heaven are in that heaven because they are moved neither by a sense of God's love flowing directly into their hearts, nor by an intellectual understanding of God's truth flowing into their minds, but by simple obedience to what they are taught about God, faith, and right living. They have no particular interest in learning about spiritual things or growing in love and innocence as the higher angels do. However, they do believe in God and are willing to follow God's commandments as they are taught. These angels are the working class of heaven.

In Swedenborg's system of angels, then, angels are higher and lower not based on some pre-created nature, but based on how fully and directly they accept God (or Christ) into their lives. This is a factor of how fully they were willing to go through a lifelong process of being born again, or regenerated, into the image and likeness of God during their lifetimes on earth.

Here is a quote about higher and lower angels from one of Swedenborg's unpublished manuscripts, which was an unfinished explanation of the book of Revelation. (He later published a complete explanation of Revelation called Apocalypse Revealed) Unfortunately, the earlier manuscript is available in print only in a rather archaic translation:

As to Michael in particular, it is believed from the sense of the letter that he is one of the archangels; but there is no archangel in the heavens. There are, indeed, higher and lower angels, also wiser and less wise; and in the societies of angels there are governors who are set over the rest; but yet there are no archangels in obedience to whom others are held by any authority. There is no such government in the heavens, for no one there acknowledges in heart anyone above himself except the Lord only; this is what is meant by the Lord's words in Matthew:

Be not ye called teacher, for one is your Teacher, Christ, but all ye are brethren. And call no man your father on earth, for one is your Father, who is in the heavens. Neither be ye called masters, for one is your Master, Christ. He that is greatest among you shall be your minister (Matt. 23:8-11).

But by those angels that are mentioned in the Word, as "Michael" and "Raphael," administrations and functions are meant, and in general, limited and certain departments of the administration and function of all the angels. (*Apocalypse Explained* #735) 

In general, Swedenborg interprets the angels mentioned by name in the Bible, such as "Michael" and "Gabriel," not as individual angels, but as whole communities (or "societies") of angels dedicated to particular functions or jobs assigned to them by the Lord. These angelic communities may act through an emissary angel. It is also possible, Swedenborg says, for a whole community of angels to appear as a single powerful angel to human eyes. (A material-world parallel to this is the personification of whole nations as a single figure, such as the figure of "Uncle Sam" representing the USA.)

Swedenborg interprets the mighty angel in Revelation 10:1 as being the Lord (Jesus Christ) himself filling an angel with his divine presence, similar to the angels who spoke for the Lord in various encounters with angels in the Old Testament, such as the three visitors to Abraham, Sarah, and Lot in Genesis 18-19. For Swedenborg's explanation of the mighty angel in Revelation 10:1, see Apocalypse Revealed #465.