It's the latter alone, I think. That, or someone gave him bad advice or he didn't think things through. He probably figured "I'm Lebron and everyone's gonna love me no matter what (wherever he goes)." Problem is in LA it's title or bust and they have guys like Kobe, shaq, Magic, Kareem who were superstars and did win titles for the team.
Should have gone to the Clippers if he wanted LA or stayed or gone to Philly if he wanted to win (and be loved).
While I'm sure that you are right, at least in part. I really doubt he came to the Lakers not expecting to win at some point.
To be fair, I doubt he saw himself missing 18 games, Rondo missing 17, Ball missing 35 and Ingram missing close to that.
The bigger problem, imo, are the rumors that top players don't want to play with him.
He's going to have to do some serious recruiting in the off-season and patch things up with the guys who are likely to be back next year if he wants the Lakers to have any chance of landing someone.