All the games apart from X-Overd were already falling apart by themselves. GK was a shitty mess of broken code, Hitsuji was doomed since forever, AS was doomed since forever and the rest were doomed too. Too few players played and paid in those games and the biggest reason they kept going so long was because nutaku took over development and kept pushing for the survival of the games.

X-Overd i do not know, but i have heard stuff like it being too f2p friendly so no one paid any money. Someone did ask nutaku why it was shut down on faesbuk and they replied that the dev had decided they did not want their game on their platform anymore.