Is there a reason people hate him? [...] isn’t he mostly known for giving away money and helping people out?

I may know why. The recently leaked PDF about how he runs his production company makes it patently clear: they aim to make successful YouTube videos, full stop.

Everything else is a side-effect. Not to suggest that they lack any ethics, but rather things like charity are there to get you to click and watch, nothing more. With enough exposure it's easy to get the impression that something is "off" with being click-bated like that. I'm not saying that behavior is deserving of hate, but it may help explain why people don't like his media.

Also, for people that are trying to make content in a much more honest fashion, Mr. Beast's popularity can be disheartening and frustrating. YouTube has clearly decided to reward this eyeball-grabbing behavior without any regards to the quality of the content. It's stuff made for the algorithm, rather than people showcasing their craft, skill, or interests. I'm guessing that people see their favorite makers and entertainers struggle to make a go of it by doing what they love, and see this guy come along and reap millions in revenue without any emotional connection to the output. To me, that's a recipe for anger.

Personally, I refuse to view popular click-bait stuff to begin with, and routinely filter such content out (click "not interested"). As a result, my YT recommendations never contain Mr. Beast content and I actually had to fire up a privacy window and click on this nonsense so I knew what the hell everyone was talking about.