Why do you think James Bond was always around a casino? Winnings can cleanly pay for hitjobs.
But in that case the money launderer doesn't even need to win, they just need a receipt showing they gambled.
https://www.theguardian.com/uk-news/2013/nov/08/gambling-mac...
This is a long lasting problem that's led to fines for the industry: https://www.ft.com/content/b90289cc-1616-11e8-9376-4a6390add...
https://www.washingtonpost.com/archive/politics/1991/08/07/h....