Steam is a "monopoly" because some devs don't bother selling their games on other stores. If they wanted to make their games available on other stores tomorrow they could do so very easily.
Windows is a "monopoly" because certain software is not compatible with other OSs, if the devs wanted to make them available on other OSs tomorrow that would be very difficult.
Epic is a "monopoly" because they are legally binding devs to not make their games available on other stores. If they wanted to make their games available in other stores tomorrow they are legally not allowed to do so.
Which is to say if Valve changes in the future and becomes shit companies and users can easily leave for other platforms.
Steam is a monopoly because if devs try to sell on other stores, they will make less money. It's a feedback loop. We buy games on Steam because all the games are there, and devs put games on Steam because all the customers are there.
Epic actually tried to get around this by offering very lucrative exclusivity deals to devs. That still didn't work.
None of that explains how "devs make more money selling on Steam" makes Steam a monopoly. Especially when as you've already said Epic has tried to pay devs directly for exclusivity as well give them a larger % of sales.
Devs make more money selling in Steam because all the customers are there. I know that accepting this means accepting libertarian philosophy is deeply flawed, but it isn't that complicated.
You argue like a libertarian, too. As in naming off logical fallacies while completely missing the substance.
I don't know what makes me a libertarian in your eyes and I don't care. The point of the discussion has been about Steam being a "monopoly", and whatever label you apply to me does not discredit my arguments nor distract from the fact that your posts have no substance other than trying to apply a label to me instead of addressing the arguments being made.
If store B is shit, and there isn't much else, then everyone flocks to store A. Then store A will be a monopoly.
If Store B is shit so everyone flocks to Store A then: