Why were there so many different churches in Pennsylvania in 1750?

Answer 1

It is not / was not that there were so many churches, as in physical buildings, in Pennsylvania but that there were many different faiths or religious sects. In fact, the number of church buildings was far less than the number of faiths because in the 1700s, worship was held in people's homes. For example, the Fraternity of German Baptists (which became Church of the Brethren in about 1907) didn't have many physical church buildings until the early 1800s, having met in member's homes for several hundred yearrs including in their home country overseas. And, technically, there were far more sects in the 1800s than ever before.

But the reason so many religious faiths or sects came to Pennsylvania in colonial times was because William Penn founded Pennsylvania to provide relief from religious persecution.