In the long term it might have a bad effect on the market, as it further helps to cement Microsoft’s control over multimedia APIs, since game developers now have little incentive now to target anything other than DirectX…

However, there are others that would argue that Microsoft's control over multimedia APIs was fully cemented since decades ago, and developers have never had much incentive to target anything other than DX since then.

Back in 2014, Valve tried to bring Linux gaming to the spotlight by offering solid and targetable APIs for developers to port their games. This approach failed hard, and most games had serious deficiencies because most publishers would rather stick a half-assed DX wrapper (like DXVK only infinitely worse) than actually do the work for a proper port.

So, with only a handful of games and what did appear was usually worse than on Windows, releases stopped coming after a year or so.

This is why we have DXVK and Proton today.

In the short term the answer is a clear “yes”, as it allows players to play nearly all Windows games on Linux without modifications, and game developers to ship their games on Linux without any extra costs.

How does that make Proton bad?

In this case it's a bit weird though, as the game lists Linux as supported platform, but obviously just ships the Windows build with Proton instead of having a native Linux build that uses open cross-platform APIs.

It being under supported platforms might mean that the developer officially supports proton and thus Linux. Hopefully they'd provide fixes if they somehow break the game on proton (e.g. they won't add an unnecessary launcher which breaks the game).

In the long term it might have a bad effect on the market, as it further helps to cement Microsoft's control over multimedia APIs, since game developers now have little incentive now to target anything other than DirectX...

You're not wrong, but people have been saying this for >20 years. We're living in that future.

Very interesting thank you!