Why did the Council of Laodicea condemn "Judaizing" Sabbath rest? The Council of Laodicea states in canon 29:

Christians must not judaize by resting on the Sabbath, but must work on that day, rather honouring the Lord's Day; and, if they can, resting then as Christians. But if any shall be found to be judaizers, let them be anathema from Christ.

Anathema, being basically excommunication, is a serious thing. Why did the members of this council consider Saturday worship a sin and even worthy of such punishment? Why were Saturday worshipers on the same level as heretics and enemies of the church?
Also, why would the church state something that is in direct contrast with the ten commandments? Calling the Sabbath rest Judaizing is one thing, but then it says to do it on Sunday.

8 “Remember the Sabbath day by keeping it holy. 9 Six days you shall labor and do all your work, 10 but the seventh day is a sabbath to the Lord your God. On it you shall not do any work, neither you, nor your son or daughter, nor your male or female servant, nor your animals, nor any foreigner residing in your towns. 11 For in six days the Lord made the heavens and the earth, the sea, and all that is in them, but he rested on the seventh day. Therefore the Lord blessed the Sabbath day and made it holy. Exodus 20:8-11

I would prefer answers from theologians and church leaders of this time. What did they say about it?

The complete canons can be read here.
Judaizer is a term for those early Christians who held that adherence to Mosaic law  was necessary for salvation. Observance of these laws (such as circumcision and the distinction of clean and unclean foods) was proscribed in Acts 15 and 11, respectively.
The New Testament distinguishes the Lord's Day from the Sabbath, and it commemorates the day of the Resurrection. While the topic has only a few scriptural references (e.g., Acts 20:7, Rev 1:10), the testimony of the early Church Fathers is consistent.
The intent by the Council in using the term Judaizer seems clear: Christianity is not just another sect of Judaism. Jews worship on the seventh day, the Sabbath. Christians worship on the eighth day of Creation, the Lord's Day, to commemorate the day of the Resurrection. Those who teach otherwise must be called out.
You can find the complete canons of the Synod of Laodicea here.