I honestly believe Microsoft missed on an opportunity to claim a percentage of the Linux market by not creating from their own Linux Distro.

This distro would have been the default under WSL. Not Ubuntu. Not Debian. Etc.

Most people would not have cared which distro. They would simply used what was provided. However, this distro would come preinstalled with Powershell, Edge, to name a few. To further that it would make it easy to install additional Microsoft software like SQL Server, Management Studio, dotnet, etc.

Simply imagine the vast majority of Windows users who have never touched Linux trying WSL for the first time and getting accustomed using tools they already know on Windows. It's likely Microsoft or their distro would gain some popularity.

While this would be common with WSL - users could also download the distro for a full install. Use what they are already comfortable with. However, if they do decide to use a different distro, they would likely have enough confidence to know how install Microsoft software on it.

Again (and thankfully) a missed opportunity.

In all, why do I care about Edge or Powershell or other Windows-based software or tools on GNU/Linux?

If there is general interest in using Edge - I, too, would like to hear it.

I imagine the biggest audience is corporate IT, especially in situations where Windows users vastly outnumber Linux and they don't really want to expend too much effort on it. Set the dev team up with Ubuntu, integrate them into whatever enterprise MDM solution they use (most support Ubuntu these days), tell them to use Edge to access the Intranet & other corporate websites, job done.

But if you just want a Chrome-y browser, you might as well just use Chromium itself. It's a bit more pernickety than Firefox (particularly if you want to have accelerated video) but it's not dreadful, and likely has first-class support from your preferred distro.