The Epic First Run programme allows developers of any size to claim 100% of revenue if they agree to make their game exclusive on the Epic Games Store for six months.
After the six months are up, the game will revert to the standard Epic Games Store revenue split of 88% for the developer and 12% for Epic Games.
The alternative back then was to buy physical games or to pirate them.
As bad as the Steam experience was at the time, it was still convenient. Nowhere else could you reliably download games at those speeds, and you could legally purchase games without leaving the house, not to mention the prices.