More sarcasm, but only because wt theology really doesn't make sense.
Jehovah is like a beaureacrat who is stuck w a mess on his hands. He can't just toss the whole thing because he made it, and so has responsibility for it. I'm not sure if it would bother him to just toss it, but others looking on would get a bad impression of him, since he is supposedly all knowing and perfect and all. He wants to end it, but he can't make up his mind as to when would be the best time, since, as you say, some always change later on. He probably wishes an asteroide would wipe it out, as that would take it out of his hands.
Back when he still had balls, when he wiped out everyone with the flood, would have been a good time to start reigning on the earth, but he wasn't ready. You see, while god had no problem killing people back then, he had a problem accepting even totally obedient and faithful ones like noah. God solved his little hangup by killing what was supposedly the best, most perfect man ever produced by humans, jesus, yet he wasn't really a human production, since all humans were sinners and jesus somehow wasn't.
Another reason god couldn't start ruling after the flood, was because he had no one who could rule for him. He couldn't do it himself, because he doesn't understand humans, his creation, well enough. Also, if he was living on earth, who would run the heavens? God can't be in more than one place at a time, can he?
SS