Paul changed a lot of things. He did away with Kosher requirements, opening up Christ to a great number of gentles, who might well have passed on him, if it meant giving up bacon or pork in general. He basically stripped everything down to Jesus and ended
most of Mosaic Law, except some parts of Leviticus, which if my understanding of Him is correct, contradicts a basic teaching of His.
As a non-Christian I view him as perhaps the greatest salesman of all time, that is not meant in a pejorative fashion. He spread the Gospel and helped plant Christianity firmly as a religion. That is no small feat. The fact that the Church endures is very much a result of the work he did, in its early days, as it were. The man was either on fire or deeply and completely inspired.
So, having all the or at least most of the laws removed, why would the gentiles want or welcome the Jews back?