@ligthert i dunno, fallen london still has 20k players. until the bill ackergeddon there were a lot of text games on f95 too.
i think the death of the MUD is in part lack of modernization (the lambda remake we're using at the moment has a web core) combined with a general lack of innovation. most of them are all carbon copies of the same diku/smaug base, or a couple coffeemuds, and the designs are some old real player hating bullshit, or just completely fumbled bags.
new haven like tried to solve the clique's having a lot of xp problem with some mechanic that causes you to get down-leveled, so you have to run plots for the game to re-earn your stats back, and through a chain of fuckups basically resulted in the grid being vented down to like six people.