If you are familiar with this American artiste you would know that he is a big time gambler or you can just say he is addicted. People are amazed he won such an amount of money in a single day but I'm not because there's a high chance that he has lost up to that amount or perhaps more than that if you calculate his losses combined. This win might actually be a way to lure people into gambling, it's very possible that the casino allowed it to happen for promotion purposes. It could be a way of advertising their casino what do you think about that? It's just a random thought, It's also very possible that he just got lucky.
As others have said, he is a brand ambassador by Stake so we don't know if he is playing with his own money or not. Second, if it is Drake's own money, then he can afford it because he is a multi millionaire as hip hop artist and businessman.
Of course during his live streams, he usually calls someone on the phone and give them money, those who sign under his affiliate. So with that they are encouraging those people who continue to gamble. That has been the norm for every streamers to attract more gamblers to the platform they promoted.