However, you are referring to the OSS community that are aware of user freedoms, software licenses... putting the end user first!
I am talking about the majority of Windows users (even tech users) who have not touched Linux. This is still a large user base.
Imagine them getting their hands wet trying out Linux for the first time via WSL. Imagine them using a default distro that holds their hand with what they are familiar with.
Regardless what the OSS community thinks, if Microsoft played their cards right, they might have gained something not just in WSL space, but also Azure.
Loads of people, even today, purposely go with Microsoft products because the business they work for supports it. Its those places that may have given a Microsoft Linux OS the chance for some percentage share.
There are people out there that are all in on Microsoft and do not care about licensing or Free/Open vs Proprietary. Some people just want to use what they are comfortable with and continue to push whatever their job covers. If there is a reason to use Linux, they likely would be happy to use a "Microsoft Distro" to keep things connected.