There have been a couple that have been let go over the years, but most mods are removed just due to inactivity. Quite a few mods seem to get burned out and just disappear. I can't blame them. Hopefully they're sat on a beach somewhere or just enjoying their life offline.
Enjoying their life?
Just curios, did theymos pay all the mods for their work or were they doing it as a voluntary job without any demand of money? If they were not getting paid, I think this could also be the reason why some of them left and got fired from their position.
I guess it's both. We're essentially seen as volunteers and not technically employees but we are paid a modest amount for our contributions based on how much we've done that month. If staff weren't paid we'd be going through multiple mods every year and despite even being paid a fair few mods do just leave for whatever reason.