They’ve more or less already done that with Proton and DXVK. Nearly all Windows games “just work” on Linux without developers needing to change anything. TBH whenever big studios develop Linux versions of games they’re usually not well-done anyway; for now it’s better if people develop with their comfy Windows tools and let compatibility tools take care of the translation. When the balance shifts to Linux dominance we can start pressing on them to learn how to use Linux SDKs.
The previous person was worried that Valve wouldn’t be able to convince “a sizable chunk of users” to move to Linux because all of the software they sell is written for Windows. If we apply a little bit of critical thinking, we realize that Valve has actually already thought of this(!) and applied a different(!) solution that solves the same problem(!) without requiring “everyone to write software for something that’s not the platform nearly all users are running”. If you want to see Valve’s attempt at getting everyone to switch to Linux without using compatibility tools you should look into how successful their Steam Machine campaign was.