It’s a fantasy as old as Genesis:

With a big enough flood, one gets to start over completely. All of Noah’s bad credit and debts, the embarrassing things his coworkers know about him, the lies he told his first girlfriend and never got around to correcting — all those vanish with enough rain and destruction.

From The Believer magazine – talking about what we are forgetting in our attraction to apocalyptic movies/literature – the aftermath is always messier than we want.