Maybe your friend thinks that he can win a big amount of money within a small period of time, that's why he's putting everything on the game. The reason why gamblers tend to lose their money that fast is because of their greed. You see, your friend had won already yet he wasn't contented and risked everything again and went back to zero. Gambling also includes smart thinking and a proper mindset. It's not just about the capital, luck, or strategy. Gamblers should also know when to stop, to avoid any big losses.
This is what I've been thinking too. It is somehow a normal story from a gambler. Winning a huge amount of money then lose it by the end of the day. I think those gamblers are blinded by winning and greed. They think they can have more after winning so much. They are feeling it and once you are feeling it, it so much harder to stop. Those who can afford to stop while winning are those who can still think critically, they are the ones who still have control. This is one of the reasons why a lot of gamblers lose so much at the point they are betting money they didn't even own.