There's probably a lot more that could be said, but I answered a similar question last year:

Did any Crusader settler's stay in the Middle East after the Crusader states were defeated?

Basically, with the fall of Acre in 1291, all the European-descended Latin Christians were dead or expelled. They went to Cyprus (also a Latin crusader state) or back to western Europe. Latins were allowed back a few decades later in the 14th century, but only in very small numbers, and pretty much only priests and monks.