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?
They claim he took advantage of their instant (no confirmation required) deposit feature. He deposited (presumably with RBF), then played and lost. He then re-deposited
using the same outputs but paying a higher transaction fee. The second deposit confirmed and he played again.
Effectively, he had already played and lost his deposit with the first transaction. He then tried to play again for free and withdraw the winnings.