What is the original explanation Christian Scholars gave for Jewish prophecies not being fulfilled? What is the original explanation Christian Scholars gave for these Jewish prophecies not being fulfilled?


  A. Build the Third Temple (Ezekiel 37:26-28).
  
  B. Gather all Jews back to the Land of Israel (Isaiah 43:5-6).
  
  C. Usher in an era of world peace, and end all hatred, oppression,
  suffering and disease. As it says: "Nation shall not lift up sword
  against nation, neither shall man learn war anymore." (Isaiah 2:4)
  
  D. Spread universal knowledge of the God of Israel, which will unite
  humanity as one. As it says: "God will be King over all the world—on
  that day, God will be One and His Name will be One" (Zechariah 14:9). cite
This question of two advents or not has been raised for near 2,000 years.  Here are some original thoughts from scholars of the first 200 years from Christ's first advent.

Clement of Rome likened the second coming to the necessity of a maturing fruit tree.


  These things we have heard even in the times of our fathers; but, behold, we have grown old, and none of them has happened unto us.”Ye foolish ones! compare yourselves to a tree: take [for instance] the vine. First of all, it sheds its leaves, then it buds, next it puts forth leaves, and then it flowers; after that comes the sour grape, and then follows the ripened fruit. Ye perceive how in a little time the fruit of a tree comes to maturity. Of a truth, soon and suddenly shall His will be accomplished, as the Scripture also bears witness, saying, “Speedily will He come, and will not tarry;” and, “The Lord shall suddenly come to His temple, even the Holy One, for whom ye look.”
  Clement of Rome


Justin Martyr explains it this way.


  And then, they [doubters of two comings of Messiah] say, the events mentioned in this passage shall happen, just as if there was no fruit as yet from the words of the prophecy. O unreasoning men! understanding not what has been proved by all these passages, that two advents of Christ have been announced: the one, in which He is set forth as suffering, inglorious, dishonoured, and crucified; but the other, in which He shall come from heaven with glory, when the man of apostasy, who speaks strange things against the Most High, shall venture to do unlawful deeds on the earth against us the Christians, 
  Justin Martyr


And the same explained it this way.


  “If the prophets had not ceased, so that there were no more in your nation, Trypho, after this John, it is evident that what I say in reference to Jesus Christ might be regarded perhaps as ambiguous. But if John came first calling on men to repent, and Christ, while [John] still sat by the river Jordan, having come, put an end to his prophesying and baptizing, and preached also Himself, saying that the kingdom of heaven is at hand, and that He must suffer many things from the Scribes and Pharisees, and be crucified, and on the third day rise again, and would appear again in Jerusalem, and would again eat and drink with His disciples; and foretold that in the interval between His [first and second] advent, as I previously said, priests and false prophets would arise in His name, which things do actually appear; then how can they be ambiguous, when you may be persuaded by the facts? Moreover, He referred to the fact that there would be no longer in your nation any prophet, and to the fact that men recognised how that the New Testament, which God formerly announced [His intention of] promulgating, was then present, i.e., Christ Himself; and in the following terms: ‘The law and the prophets were until John the Baptist; from that time the kingdom of heaven suffereth violence, and the violent take it by force. And if you can2110 receive it, he is Elijah, who was to come. He that hath ears to hear, let him hear.
  -ibid- chapter LI


Basically, Justin Martyr is arguing from Scripture about two advents.  The first was about Messiah inglorious, suffering death, generation not declared, but the second in glory with all looking on Him who was pierced.


  Then I [Justin Martyr] replied to him [Trypho], “If, sirs, it were not said by the Scriptures which I have already quoted, that His form was inglorious, and His generation not declared, and that for His death the rich would suffer death, and with His stripes we should be healed, and that He would be led away like a sheep; and if I had not explained that there would be two advents of His,—one in which He was pierced by you; a second, when you shall know Him whom you have pierced, and your tribes shall mourn, each tribe by itself, the women apart, and the men apart,—then I must have been speaking dubious and obscure things. 
  -ibid- chapter XXXII


Lastly, Tertullian will make the same arguments from Scripture.


  We [Christians] affirm that, as there are two conditions demonstrated by the prophets to belong to Christ, so these presignified the same number of advents; one, and that the first, was to be in lowliness, when He had to be led as a sheep to be slain as a victim, and to be as a lamb dumb before the shearer, not opening His mouth, and not fair to look upon. For, says (the prophet), we have announced concerning Him: “He is like a tender plant, like a root out of a thirsty ground; He hath no form nor comeliness; and we beheld Him, and He was without beauty:  His form was disfigured;” “marred more than the sons of men; a man stricken with sorrows, and knowing how to bear our infirmity;” “placed by the Father as a stone of stumbling and a rock of offence;” “made by Him a little lower than the angels;” declaring Himself to be “a worm and not a man, a reproach of men, and despised of the people.” Now these signs of degradation quite suit His first coming, just as the tokens of His majesty do His second advent, when He shall no longer remain “a stone of stumbling and a rock of offence,” but after His rejection become “the chief corner-stone,” accepted and elevated to the top place of the temple, even His church, being that very stone in Daniel, cut out of the mountain, which was to smite and crush the image of the secular kingdom. Of this advent the same prophet says: “Behold, one like the Son of man came with the clouds of heaven, and came to the Ancient of days; and they brought Him before Him, and there was given Him dominion and glory, and a kingdom, that all people, nations, and languages should serve Him. His dominion is an everlasting dominion, which shall not pass away; and His kingdom that which shall not be destroyed.
  Tertullian


There are other people who explain the two advents in the same way.  The first is as the suffering servent and the second is as the King of Kings.  But this should suffice to answer the OP questions.

PS The temple is believers indwelt by the Spirit (born-again).