I think possibly one of the goals of Proton is to allow for a gaming streaming service like Stadia without needing to pay the Microsoft tax, or to tweak the Linux kernel in other ways as to increase RoI.
The goal of Proton is probably to have an alternative ready in case Microsoft decides to go Apple and require 30% payment for everything that runs on their OS. They started to lean that way with UWP and Windows Store and it made Valve work on Linux compatibility since.
Wishful/Crazy thinking?