He sees people forgetting and cursing the Gods, and he also suspects Hades of treachery. He knows he can't move against Hades without the rest of the Pantheon's support, and they won't believe him without proof. So he sics Hades on mankind, supposedly supporting him against other Gods in his efforts to humble man. He secretly helps Perseus, and then, in the final battle, Hades demonstrates his desire to take Olympus, Zeus either comes out to battle him or shows the world Perseus' God-given weapons, and is able to get rid of Hades, and since Hades was the bad guy, everyone is grateful to Zeus for getting rid of him, so he regains his power.

But, that never really happened. Instead, Zeus helps Perseus all through his quest for no good reason.


And I assume the Stygian witches suffered from all the editing? Perseus never died, never really came close. He didn't die to be brought back by a God, he didn't get saved at the last minute by a teammate taking an arrow for him or pushing him out of the way of a falling rock. The witches straight up lied. Unless they just meant he'd die of old age.