The protest is being driven by the moderators who do the free labor. They are being mistreated by not being able to use the 3rd party apps that make their (unpaid!) job easier.
Reddit, now seemingly desperate for money, decided they needed to jack up the API prices. This is after squandering a fortune on VC on a bloated dev team making stupid features like NFTs. If they hadn't blown so much money and created an expensive wasteful company, they wouldn't find themselves in this situation.
Now they're dumping on their most valuable users, the unpaid moderators to squeeze anything from the bottom line.
It's disgusting, and I'm done with Reddit. I deleted my 8yo account. I hope the CEO gets fired and it burns to the ground. Hopefully something better rises from the ashes.