From my understanding, MrBeast is doing what a lot of copycats are now doing.
Basically, he was just giving away money-holding contests and just kind of created a large community that translates into a big subscriber base, and it kind of snowballed from there.
I've seen smaller YouTubers pull this off with some varying degrees of success.
But the more you figure out what your community is into and incentivize them by holding contests, giving stuff away, or letting them direct you as to who to give money to, the word does spread out.
And don't be surprised if your subscriber base starts blowing up.
Since this model is kind of getting beat to the ground, I'm not convinced that it is a sustainable model because how may MrBeasts can YouTube sustain?