I never saw or heard from him again. 

Most addicted to gambling know they have a problem and perhaps even regret every time they vow to quit.  Your ex client had his moment of reckoning when he thanked you.  Then he probably lost another $250K and decided not to face you.   You tried to help him but instead helped yourself lose a client.

Perhaps he's now the fund manager for Fidelity's upcoming Crypto Retirement Fund.