I'm sure stake is not stupid to give that amount to Drake if they are not expecting a return from it. Drake is like an NBA star who wear shoes for sponsorships and receive millions of money, hopefully, that would bring success to stake as they have invested a lot of money from this deal.
Obviously endorsement is not stupidity at all, Drake is a celebrity know in the world, endorsing him will help Stake to bring more customers which will help the gambling site to earn more money as well. It is win for win.
maybe drake will not be able to draw enough people to their casino to produce those profits immediately, but if it gives them and advantage over other cryptocurrency casinos then they may eventually recover that money in the future.
With what I have noticed about gambling, stake is not the first gambling site that make use of celebrity for promotion, gambling sites that had used celebrities in the past were able to get more customers registered and increase in gambling activities, the more people played the more the losers, the more the growth of the gambling site. Endorsing Stake will work for them.