Normally it's very possible we may not get to know the personalities some persons have got beyond thst which we know until they later get some where else and do better,  lest not forget he role of environment playing out on the personalities of certain persons, they may be at a point where they literally want to exit or want something but not getting it in a particular environment may frustrate their efforts and cause them reacting and behaving in certain ways of which I believe was the case of mbappe, now at Madrid that appears like his dream, he's doing just fine with them. Like you rightly stated too it could be the power he had at PSG which he no longer has at Madrid so all these put together are factors to consider.