There are a few layers to it. I’ll start with the legit reasons and hope the jackasses don’t read too deep in:

1. EGS was built around the idea of providing what people need/want rather than EVERYTHING. Some of that was truly asinine (no shopping cart for like 2 years?) and some was a conscious choice based on everyone saying they don’t want their video game store to be a social media network. Unfortunately… people apparently DO want their video game store to be social media.
2. Every store handles regional pricing and distribution differently and, allegedly, EGS had worse coverage in a few of the countries The Internet actually knows exists.
3. Tim Sweney is a complete and utter dipshit and always has been and it is REALLY hard to not hate everything he touches.
4. EGS rapidly entwined itself with Fortnite because Fortnite makes more than the GDP of some small nations. But we are hardcore gamers so we all hate Fortnite.
5. Sweeney/Epic actually accidentally argued for consumer rights against Apple which, in turn, led to the full force of Apple running smear campaigns against Epic to make sure that we all realized how much we love walled gardens
6. Sweeney/Epic ALSO kind of picked a fight with Steam by pointing out how little developers get from any given sale. Which… because we all love Valve means that Epic are assholes and developers all actively want to strive to get the negotiating power of a Call of Duty or Rockstar.
7. Speaking of. EGS isn’t Valve and any alternative is inherently evil because we all love Valve.

So what was a mediocre store with a lot of free games and a tendency to give developers a giant sack of money for one year of exclusivity became The Devil.