How did he attempt to cheat them?
He deposited played and won, how is this a cheat?
Is he accused of manipulating the gaming software?
Stop acting stupid. This is likely what they did:
1. Deposit X BTC at a low fee
2. Sportsbet credits some withdraws with 0 confs, and in this case it was likely credited
3. Go all in on some casino game/sports bet
4. Double spend if loses, allow confirmation if won