This user claimed to have won $900000 from offshore sportsbook.
However checking his past post history revealed the actual truth.
This guy had been betting from USA using VPN and fake ID!
Consequently no casino would provide him with official betting history and documentation. lol

I don't understand how this allows the exchange (Coinbase) to steal his money

Why do people think it's normal for someone to make a deposit, and then, in order to get it back, they have to dance like a clown and do a million things to prove that these are their funds and that they didn't violate any laws 200 transactions ago?
I certainly understand that there is some regulatory rule requiring (or permitting) the exchange to act this way, but that doesn't stop me from considering such actions fraud.