The things that cause AUs to die quickly

So, I only rp in AUs and I've adminned a lot of them too

The biggest issues I've found with AUs (specifically the ones that die out quickly, this is in no way talking about those AU roleplays that are doing really well and succeeding and have sustained activity for a loooooong time) are the following:

Inactive admins
I'm hella guilty of this myself and I've noticed it in a lot of places, and this is when anyone on the admin team is inactive or is only active in OOC rooms and such. Even if there are, say, 3 admins and only 1 is inactive, it gives off a bad impression to people joining the roleplay that want to roleplay. It makes it seem that the admin doesn't care, and then when they don't meet the activity requirements and they don't get kicked because they're an admin, it makes others feel as though they don't need to be active either, and what's the point being active if the admin isn't.

Liking the idea but never roleplaying
A lot of players join roleplays because they like the idea of the roleplay, and the idea of building characters for that roleplay, but they never get around to roleplaying because either once they join the roleplay they realize it was only the idea that they've liked, or they spend so much time building their character that when they're ready to RP, most other people have either left because they got tired of waiting to roleplay. or other people are still working on their characters, or everyone is knee-deep in plots with other people and don't have time for other plots.

So please, if you're an admin of an AU, keep yourself active and remind your fellow admins to keep active, and to regular players, you don't need to spend a month developing every little part of your character and noting it down on your profile. It can be just as fun to reveal the details through roleplay, and then you'll know exactly what isn't necessary to put on your character's profile.