I'm also a fan of esports, having got into Rocket League a couple years ago. It's quite interesting the difference. There are professional players there, but I've never quite understood how esports works - it feels like a VC funded Ponzi scheme that will implode some day. Like, how are all these Rocket League players getting paid?
The difference, I think, with disc golf is that to play, you actually need to buy some physical things (discs), and those will eventually get beat up from hitting trees and concrete, or you'll lose them, so there's constantly people out there spending a bit of money. (Not a ton, mind you, and that's part of what I love about the sport; the vast majority of courses are free! Just a walk in a park, basically.) And so these disc manufacturers can afford to sponsor some pros and so on.
I imagine the Paul McBeth deal is so big in part to be splashy and bring attention to the sport, but it's not so outlandish to me like with esports.