You showed up with lets say $50k at the casino, you departed with the same $50k. If you'll be investigated, you still can't justify the money you walked in with.
Criminal 1 buys $50k in chips using wired funds. Gives chips to criminal accomplices 2, 3 and 4.
CA2, CA3 and CA4 come into the casino a few different times over several months, gamble for while for a net zero gain or loss, and then convert their "winnings" from chips into cash in chunks of $5k or so - flying under the radar.
C1 never needs to come back to the casino where the police might catch him - and he is the only one who is linked to the big heist.
You showed up with lets say $50k at the casino, you departed with the same $50k. If you'll be investigated, you still can't justify the money you walked in with.