I am not saying the umpire is to blame or that he is not to blame for the weather part (I do believe he is absolutely culpable for the lack of game management) . . .
I am just going to say that, while the rulebook bestows the authority on the umpire to determine whether to play or suspend, there can be other factors exerting influence.
Speculating here, but I'm guessing he was operating without certainty about whether they would be able to re-start if they suspended play (i.e. is the rain going to continue, and if so will the game ultimately be called).
If they couldn't continue, score reverts to last complete inning, and the appearance is that LA gets "screwed". But if he let's it play out, Cal clearly is disadvantaged and Cal gets "screwed".
I believe the right thing to have done would have been to suspend play, endure the yelling that you'd inevitably receive from the LA coach, and hope you're able to restart.