For people who need Windows for some business requirement, this lets them use less Windows, and have a Mac or Chromebook as their hardware. The result: less Windows.
For people who don't currently use Windows, does a slower, internet-only Windows present a compelling product? Windows doesn't really sell itself (other than as a gaming platform, but we have Nvidia's streaming platform for that), it's a default but if you've not got a business need most people either already have Windows (because the PC was cheap or they play games) or they aren't going to go looking for Windows.
As Windows becomes more and more of a platform for ongoing revenue (read: ads, subscriptions), it's likely to become less attractive for that second group, and that first group will spend less time with it (and see fewer ads).
I get that on-demand cloud machines make sense for many businesses, but I'm not sure that aligns well with my (very naive) understanding of Microsoft's priorities here.