This is basically a question about
1. Is it possible to create the conditions where people in Spain continue speaking a Romance language but mostly convert, resulting in a modern-day Spanish-speaking Muslim-majority country (the whole peninsula, or even a small part of it).
2. If it's deemed as too difficult, how does it fundamentally differ from Bosnia or Albania, where people kept their native language but changed religions?
I would really appreciate help on this. It's a question that's been bugging me for a while.