I feel confident in guessing that any net changes in Windows popularity have close to no relation to Microsoft's policies around trusted CA. The number of users who are worried about sketchy certificates being trusted by default are dwarfed by the number of users who don't have any idea what a "trusted CA" is but care about more "visible" things like UI changes, performance, and how hard Windows is pushing Edge and other things they don't want.
If the rationale in the parent comment for this behavior is correct, it sounds like a lot of people making the decision to use Windows are doing it _because_ of behavior like this, not in spite of it.
I looked at the graphs at Statista. I don’t think it’s so clear cut. Mobile OSs have pushed it down, but it seem to dominate PC market. Do you have a graph that shows its decline on computers, not mobile phones? Or in absolute unit counts?
I think that might be a bit of an unfair caveat. People do real work on mobile OSes. They shop and communicate on mobile OSes, and occasionally organise revolutions.
(Although I'm not sure why "Netraft confirms, Windows is dying" is a useful comment here anyway. Windows is a behemoth.)