One thing all addicts have in common is the belief (from repeated pattern of thinking) that "using" will make them feel better.
This belief starts in the early stages of addiction when all of us enjoy using our drug. The more we enjoy using the more the belief is reinforced that using makes us feel better.
As addiction progresses we don't feel better when we use but the belief remains in place and we are ever using more and more to make us feel better.
For the lucky ones the losses in life due to the addiction eventually break through the belief that the drug will make them feel better and they hit rock bottom......hopefully change the belief that using makes them feel better and they go on to recover.
The way I see it with this situation is that this win has not only reinforced the belief that gambling makes him feel better but also that now gambling does not lead to any losses in his life. So instead being near to where he could have reached rock bottom, he could be further away.
Even if the money goes very quickly, that belief that gambling makes him feel better is real in the not too distant past rather than way back then in the early days when he started. In my opinion, recovery will only happen when he believes differently.