I'd be the first to admit that I don't exactly know much about this topic and the initial research I've done on it has simply led to greater confusion. My current understanding (which I'm pretty sure is wrong) lies around the thought that feudalism was in decline due to the changing nature of Europing becoming more "centralized" and needing less fragmentation. 

What I said above should've hinted that my knowledge is extremely flaky so if possible use pleb terminology. :)