Christianity was quite successful in Isreal until the diaspora.. When it REALLY began to spread.. like wildfire.. The pagans could'nt murder them fast enough.. It still spread..
Jews then were never really populous, anywhere.. Wonder how many Jews became Christians for the last 2000 years.. Not to speak of the fact that you can be a Jew and a Christian at the same time.. many Jews were Christians also.. Even today some Jewish familys will disown and shun a family member for becoming a christian..
Oh, what a joke! There is no historical record of any massive Christians anywhere in Israel. There are no historical records of Jesus, His ministry, His trial, or anything. And pleas don't bring up Josephus, because his "reference" is doctored and corrupted in several versions.
Christ commissioned His apostles not to go to the Gentiles, but only to the tribes of Israel. They weren't terribly successful. And even Christ predicted that they would be thrown our of synagogues (it's in the NT).
As far as pagans murdering Christians, Saul was no pagan, he was a Pharisee. Obviously, the Jews were doing well hunting down their own apostates and killing them.
The Church in Israel was literally dying. The only way it was going to survive was to convince pagan Greeks and Romans by including them in the Gospel.
There were quite a bit of Jews in Diaspora dating back to the Babylonian capture of Jerusalem. Alexandria and Asia minor were full of diaspora Jews who no longer spoke Hebrew but Greek for centuries. There was also a large colony of Jews in Rome.