So we know what he stands to lose, what does he stand to gain?
If he is currently doing badly, many of the losses will really be gains. For instance if he is losing money, quitting professional poker can't be a loss to him. He can still play recreationally anyway.
I read a bit about him and he has a "book" and this can't be a bad thing for promoting that. This bet certainly got me intrigued. Reading interviews etc, he certainly has a destructive streak with his gambling, so this doesn't even look out of line and losing this challenge isn't going to put him in a position he hasn't been in before and may even be good for him in the long run. I am not claiming it is definitely a positive, just it may well end up that way.