The argument that Proton purely drives Linux adoption without disincentivizing native development ignores how publishers behave in reality. Instead of inspiring studios to eventually target Linux as a primary platform, Proton gives them an excuse to ignore the platform entirely while washing their hands of compatibility when updates break things. There are already SEVERAL cases where developers have pushed updates to games that worked in proton previously but no longer do. For Honor, Rust, Apex Legends, GTA V to just name a few. When developers treat Proton as a convenient accident rather than a target, it doesn't pave the way for a native future. It creates a volatile ecosystem where a single background update can permanently strand players on an unsupported island, with the studio refusing to spend a dime to fix it. Proton keeps Linux users as second class citizens.

In the couple of years before Proton took off games with Linux support was at an all time high, companies like Aspyr and Feryl Interactive helped studios port their game.

Proton has killed off official Linux support and the industry around it for better or for worse.

Probably not it is easier to develop for Windows. To many variations in Linux installs. I have native Linux ports of games bought decades ago that no longer work. If I had bought windows versions they would still run.