In terms of people who might consider Fusion you have:
- People who only use Windows
- People who only use macOS
- People who only use Linux
- People who virtualize Windows on macOS
- People who virtualize Linux on macOS
- People who run FreeBSD or similar on their computers
- People who virtualize FreeBSD or similar on macOS
- People who virtualize various operating systems on Windows
- People who virtualize various operating systems on Linux
- People who virtualize various operating systems on FreeBSD or similar
And I would guess that the largest group of people that use Fusion use it for running Windows in a VM on macOS.
I would guess that the people who develop for Linux servers would mainly use Docker if they run macOS, and that also relies on VM, but not using Fusion.