CityRPG hosting is literally draining.
You need a strong team of Admins who you can rely on and that are fair, servo had a couple of bad eggs which slowly made the server unpopular, you've always got people asking how do I do..? how do I get a job? can I be a..? can you give me..?
It is a lovely mod to work with, but it does have loads of tiny bugs which can make it difficult to work sometimes. As an admin you're forever explaining stuff to people, dealing with some person who just ran over someone in a little pum pum car and has made the other person loose $6k from dying with it on their player.
I think the main reason it dies out so quickly is because it does take a stuff ton of maintenance and a team of reliable and fair admins who are active regularly who carry out the role properly