Why did the catholics settle at the Plymouth colony?

Answer 1

Catholics mostly came from Ireland, some as slaves. From the Catholic Encyclopedia:

Catholic colonizationThe Plymouth and Massachusetts Bay Colonies were composed principally of English. Near the close of the reign of Charles I, however, the forced emigration of the Irish brought many of that race to these shores; their number is hard to estimate, first, because the law made it obligatory that all sailings must take place from English ports, so that there are no records of those who came from Ireland with English sailing registry; secondly, because the law, under heavy penalties, obliged all Irishmen in certain towns of Ireland to take English surnames--the names of some small town, of a colour, of a particular trade or office, or of a certain art or craft. Children in Ireland were separated forcibly from their parents and under new names sent into the colonies. Men and women, from Cork and its vicinity, were openly sold into slavery for America. Connaught, which was nine-tenths Catholic, was depopulated. The frequently published statement in justification of Cromwell's persecution, that the victimes of this white slave-traffic were criminals, finds no corroboration in the existence of a single penal colony in this country. In 1634 the General Court of Massachusetts Bay also granted land for an Irish settlement on the banks of the Merrimac River.