Its not really a change in personality, its more of "I'm sick of your crap and destruction, you rotten humans". "I tried to show you how to behave to please my dad but you just refuse to listen."
Mankind was shown a better and more peaceful way ... but we just kill and kill ... subjugate and kill some more. Pollute and kill. Certain types of folks ( the ones that like to kill) just have to go if there were to ever be a real peace on this crazy planet.
Notice how he became hostile with the money changers inside the Temple? Notice the temple was split at its foundation at his death? Notice how Israelis today do not have the Arc or a Temple?
My opinion, of course.