Not even Cyberpunk or the Witcher could sell more on gog than on steam even though you knew that there the developers got 100% of the money spent.
Most gamers don’t know and/or don’t care, so they will take the least resistance path, which is Steam.
Steam has a “most favoured nation clause” which prevents companies from actually selling for cheaper on other platform. This is how steam maintains its monopoly. If it were possible for CD Projekt Red to sell it cheaper outside of steam it would force steam to actually charge developers less.