The reality is, while reddit gave API access for free, they paid for that, while the dude who created Apollo made millions, thanks to reddit. He's not some small mom and pop shop that got squeezed out by some big bad corporation. He was lucky he took advantage while he did. And quite frankly, he tried to extort reddit also.
Exactly this.
First, Reddit is a business. It has employees, it maintains servers, it has costs and bills. Why should others be able to profit off of Reddit’s work without some kind of compensation going to Reddit? This stuff can be pretty expensive to maintain.
Second, it’s never great to rely on another company for the soul survival of your own business. A day will come when YouTube will dramatically change their policies and a lot of full-time YouTubers will suddenly find themselves out of a job. The problem is they never think the current deal will go away, so they have no back-up plan. The same is true for any developers living off another company’s API.