Originally Posted by aydee
They can be defense mechanisms, protective shields, masks to cover up low self esteem etc
That certainly explains why the more successful drummers (or actors, artists, etc.) tend to not have an overblown ego: they're secure with their success. But that doesn't necessarily preclude someone from being unpleasant or hard to get along with, and there are musicians, actors etc. who have poor reputations. But it's not an ego thing, it's just their personality, and would exist whether they had artistic success or not.
There are exceptions of course, and defending bad decisions by saying success went to their head is a favorite excuse. But those types are far outweighed by more modest, grounded, 'nice' folks.
Typically, those who deserve an ego are the least likely to have one. And all to often, the opposite is also true.