It's a "gigantic win" for everyone in the same manner that Uber paying drivers and customers (via bonuses / free rides) to use their service was one for everyone involved . Sooner or later, Epic will have to stop doing this once they get their market share and there is no guarantee that this will be the financial model they follow (free games frequently, paying devs to be exclusive etc).

It works in a different context ( platform exclusives ) because the lock in / costs to developing for a different platform are far different from that for different stores on a single platform.

Good for dev. Even good for end user since they are throwing money into easy bait like offer free things to user just to use the platform.

But I would refrain from investing much more into the platform since what Im seeing right now isnt going to sustain the platform in the long term.

Its one thing if the store has distinct feature like gog, but theyre not. In the end I(and many others surely) use it just to get free games.