Yeah, European diseases wiped out 95-98% of the Native population. That basically destroyed their culture and economic infrastructure, and at least 50% of the tribes were totally wiped out completely. As most tribes had no writing system, the word of mouth knowledge accumulated and passed down for tens of thousands of years was mostly, and almost completely lost. Those tribes which did have writing systems had almost all of their writings burned by Cortez and other religious fanatics who believed they were doing "god's work".

I always wondered about the term "god's work"... I mean should an all powerful being be able to do his own work?

@snytiger6 Apparently, ONE CATHOLIC PRIEST, conscience-stricken, saved a copy of the Popol Vuh...which is all we have now to study the religious beliefs of the Maya people.