I would've had the same reaction a few months ago, so here's a brief summary for us olds (since every English speaker between the ages of 10 and 18 seems to know who this is):
Mr. Beast gives away, or otherwise spends, enormous amounts of money in his YouTube videos. The reasons for giving/spending are often wrapped in a kind of gameshow format. E.g. his most viewed video (at over 200 million views) is a Squid Game clone during which he gave away nearly half a million dollars.
To me, this is most similar to Silvio Santos[1], one of the wealthiest men in South America, universally beloved by the elderly population of Brazil. Santos' brand is being a respectable, Christian man, who happens to be very generous. When I was young, I didn't understand the appeal, but of course I wasn't the target audience. The case of Mr Beast is very similar, but the branding is targeting young people.
I guess a potential American analogy is Oprah? On any given episode filming, anyone in the audience could've gotten a new car or something.
Google bought the whole of YouTube for only $1.65bn (though in 2004 dollars)