Valve has little control on what other companies target. Their previous push for native gaming produced very little results: Valve ported all their titles, a few minor publishers released native titles and some porting companies ported some AAA titles, but it was only a drop.

Proton has caused a significant increase in Linux playable games. The side effect is that it effectively killed porting companies.

edit: also all porting companies were effectively using their proprietary equivalent of proton (although often inferior) .