Well, if P1 is week tight, shouldn't he fold at this point?

In my mind, the ladies don't look so good now. With all those callers, the chance of one pair holding up, especially when that pair is not aces or kings, to the river, isn't good. Even if the raiser is bluffing, you don't know that the other callers didn't hit big. If P1 had position, it would be one thing, but he doesn't.