Players.
The crux of the matter: I feel like Doc is too nice a guy to actually lose his mind and dig into the guys, imploring them to actually run the offense in key moments and/or play within a system...Not that that would be a winning strategy, as KG, Pierce, Ray, and Rondo would have none of being exhorted or criticized. Essentially, this is a deeply flawed team with ego issues.
Doc is actually rather well known for not caring about the egos of his players, and digging into them when they screw up.
Seriously, where are these ego issues? Rondo is the only one who is anything close to a headcase, and even then, all the mutterings on the Internet about how difficult he is are extremely overblown. KG and Ray are both well known for being team-first (KG to the point of an obsession). And Paul Pierce was once known as a selfish player, but has visibly and publicly matured since the Big 3 era.
Honestly, where are you getting this armchair psychology from?