Yeah, it would be interesting to know how he got so powerful himself. All those hundreds of other monks must have had powers since they were using them at the end, yet Jet Li's character had to go around dealing with the demons by himself (except for a comedic sidekick)? Even if he was so powerful he'd never failed, there was plenty of room for collateral damage without teamwork. As we saw at the end, White Snake was able to flood the whole area. Lawsuit! In reality, great care is taken to avoid the need for heroics, but in movies like these, they try to create lone heroes or heroines up against great odds. Maybe none of the other monks cared if demons inhabited the world or thought it was worth taking them on. We never heard a word out of them, anyway.
Jet Li's character's attitude, though, reminded me of the detached "That's just your addiction talking" style used by those who deal with addicts, though (White Snake could be seen as a love addict.). That aspect at least rang true and could have led to his downfall because he was so fixated on being oppositional to whatever White Snake said that he stopped being reasonable. But that White Snake would so quickly announce she was just going to flood the place and probably drown her precious herbalist was ridiculous. What did White Snake think was really going on? They were holding her herbalist prisoner just so she couldn't get to him? That they were going to kill him? If so, she should have said so. And then at the end some divine "merciful" power suddenly appears to give the command to give her one last chance to see him. Gee, that would have been more helpful if it had come about 10 minutes earlier before she drowned half the town. Let's see some beatings, stabbings, and drownings, before being merciful. Weak excuse to have the big showdown at the end typical of these movies, where its like "Ok, finally, we don't have to write any more story! Insert a bunch of CGI fights. THE END" You could look at it like it was just a diversion for the rat demon to get in, but they don't do anything to convey that.