'Reddit finally finds a way to become profitable' is not what's going on. Reddit's own claims are conflicting, they simultaneously argue that other apps are causing them massive losses in terms of opportunity cost while arguing that they represent an insignificant portion of users. They've argued that the apps are too inefficient in their API usage while their own app is no better, and despite their claims, they demonstrably haven't tried to actually work with app devs to resolve this.
On top of that they're making these changes without having addressed the issues the 3rd party tools exist for despite having promised to do so for many years now. Them later backpedaling and attempting to carve out special exemptions for those only makes them look worse.
It'd be a lot less egregious if they were like Twitter and just said the obvious about how they didn't want to allow 3rd party apps anymore. Instead they're engaged in this scummy game of lies about how they really want to work with the community, so it makes perfect sense that the community is opposing them.