Just out of curiosity: how do they detect cheaters?
Do they find that he plays too good for his rating?
The site does not disclose the methods used, for obvious reasons.
Discussions of cheating or cheat detection are no allowed in the general forums. If you want to have that discussion, join the following club:
https://www.chess.com/club/cheating-forum
https://support.chess.com/article/648-what-do-i-need-to-know-about-fair-play-on-chess-com
At least they were not sited for violating Chess.Com's Foreplay policy...............................