This is really a theology question. So you might be better off in an alternate subreddit. Unless you wanted a specific answer about Christianity in a historical period, which would be historical theology.

the reason for this comes from the Council of Jerusalem.

The Council of Jerusalem was the first council (in which all other ecumenical councils would be based on) of early Christian church, it was meant to decide the Gentile Question.

Originally when Jesus was teaching, alot of the apostles were Jewish, and many considered Jesus' teaching NOT as a new religion, but as a new era in Judaism, Jesus was the Messiah that was promised by the prophets, it only made sense that Jews continue this belief.

It was not until Paul the Apostle's teachings, and his interactions with gentiles, and anyone that was willing to listen, that early Christians ever considered it expanding to non jews. Its not that they weren't wanting converts, its that they believed Christianity was a continuation of Judiasm and therefore followers should be Jewish first.

Since Paul's teachings seemed to be so successful, Christian leaders were seen at a dilema, they had all these people who wanted to follow Jesus' way of life, but had no experience or practise being Jewish. What should they do about them?

Paul's opinion was that Gentile's should not have to be Jewish in order to believe in the Messiah, and that Jesus' teachings would be more successful / helpful if people did not need to follow Jewish practises first, these included adhering to the Torah, Jewish holidays, dietary requirements and the biggest issue of all getting circumcised.

On the other side of the table James is said to have firmly believed in the old covenant, and to fully understand Jesus' teaching, you would need to keep Moses' law.

Overall, after much deliberation and discussion with all those attended, including Peter it was decided that Jesus' teachnigs and message was the most important part of this new movement, and following the teachings and lessons of Jesus was enough. This was particular because as Paul argued, Jesus was the new covenant, and the only covenant that mattered (the last supper, communion etc.)

Finally it was the agreed upon that Gentile's should not be punished by their local customs and freedoms, since Jesus taught about loving thy neighbour, and Christianity should not take the liberties of a man, however they should try and follow Jewish practises when it does not interfere with any of the above.

It should also be noted that, without modern medical practises, circumcision of an adult male is alot more dangerous then a baby / child.

So in the end it was decided that because of all the different cultures of the Gentiles, it would be unfair of them to conform to one, as long as they believe and follow the teachings of Jesus, they should follow Jewish practises, however ones that were very life changing (dietary and circumcision) were seen as optional.

As read in the Acts, "We should not trouble the Gentiles who are turning to God"

This decision however was not without objects / different interpretations / anger between different factions, although for the most part, it was accepted

Overtime different practises have fell away / been adapted (Catholics still count good friday as a day they can't eat meat, similar to the passover celebration, circumcision optional etc, baptism comes from Jewish baptism) and the church steadily broke away from its Jewish routes.

EDIT: As other have said, there are some major theological debates going on as well, however I focused on the secular, historical event side, as seemed apporpriate for this subreddit.

Like talondearg says, this is really more of a theology question. It happened quite early in the history of Christianity, much of the new testament is about this question. If you're interested in the primary arguments, I'd recommend starting with Romans or Galatians, or another of Paul's letters.