User blog comment:Omgitskittykatty/Things You Probably Didn't Know Until Now: One Hot Minute/@comment-24574398-20140727082253

Lol everybody ignored this. The answer:

Mostly because of Navarro's drug addiction (that was no different from what the Peppers have seen and did before) and musical differences, but Navarro crossed the line when he fell over a lamp and broke it while on drugs.