Hi-Rez shot themselves in the foot with how they managed the game. Unbalanced weapons always released; screwed up hitzones, layout revisions, messed up admin abilities for server renters (since you can't own a server), the list goes on and on and on. A lot of us Tribes and Tribes 2 fans were and are very unhappy with Hi-Rez's mismanagement. It had a lot of promise, but this is what happens when they become too focused on making money and not satisfying their customer base: A dead game.
P.S. While there may have been a lot of eGO members who downloaded the game, there never was any set group gaming night or serious/hardcore dedicated group of players. I think that's what led to its removal from Op:X