mco under current management rose by 100-150 players approx during peak times and after a major update. Mco under mine and prior managements rose from 300-400 players at peak to 900-1k players at peak, settling to 700~ off peak times. Judging by that, it was a good decision to leave as the server's current management is not up to par with prior, and the players likely feel the effects of that, and choose to go do better things with their lives than a minecraft server in 2018.
Another little note is, there have been servers with prison for years, had time to perfect it and be better than all the others. Not saying it's impossible, just really unlikely what mco will pull out is anything special enough to choose it over all the others.