What I don't understand is why Canonical thought that shrinking their user base would be good for their business.
As developers, we're all enthusiasts of the WSL and how we don't need to dual boot, run VMs etc. any more. But in the process, we may end up giving less love to our once beloved DEs. This in turn creates a negative feedback for Linux desktop adoption. Also, less bare-metal installs means less bugs discovered and ironed out in the kernel too, less incentives for developers to release drivers, etc. so in the long run it's going to hurt Linux much more.
The only user base that shrinks is the Linux Kernel user base; Ubuntu and Linux are two separate concepts, and WSL demonstrates that they are in fact fully separable.
I don't think this business model will last much longer, though ;-)