Eh, I think colonizing most of the Islamic world had a significant amount to do with it.
Britain's mistake was allowing religious liberty to trump constitutional liberties via Sharia family law courts.
France's mistake was their ethnocultural snootiness that led to significant disengagement by Muslim youth.
Germany is actually a "success story", if such a thing even exists, when it comes to Muslim integration in Europe. But that's a relative term, obviously.
None of them have done as well as Canada and the U.S. have done, though.