Its interesting phenomenon. Probably a mix of reasons causes it - ego, too much self confidence, lack of brain in some, wrong ideas, corruption, greed ... some more

Take Roger Ver for example - he probably thought of Bitcoin as his ownership, as being able to take better decisions than Satoshi Nakamoto, having certian greed probably too and huge ego.

He turned complete shitcoiner by creating b-cash and writing his book "Hijacking Bitcoin" when he is the one that tried to hijack it.