Why do gods do all of that? Well, I guess immortality is rather boring; the poor dears have to occupy themselves in some way. And seeing all the same faces centuries after centuries is not interesting enough. Nor is blasting away mortals and making them die in all kinds of imaginative ways. That too becomes boring after the first century.
What the gods ended up doing is play an elaborate game against each other using mortals as pawns. The general idea is to get many mortals to
pray for them specifically. This is, of course, for their ego and to improve their rank in their own social hierarchy, but they also get a small boost of power from it. One mortal alone is insignificant, but once they get whole countries to worship them...
So, the gods all play their little games, showing off to the mortals, building their priest-minion cults, vying to become the official religion of empires... before throwing it all away on a whim because that man over there was rude, and washing the insult away with fire—and the whole country with it—was far more important. Priorities, you know...