Actually as I think about it it might not be so strange what you're seeing.
Fusion 11 is unsupported on macOS 11 and 12 so it's understandable that it won't install. Those macOS releases made a lot of changes under the hood/bonnet which had to be addressed in Fusion 12.
While Fusion 12 is unsupported on Apple Silicon, it will install - as you found. The GUI portions actually will execute (their Intel code will run under Rosetta). It's just when users try to run a virtual machine that the unsupported part rears its ugly head. The virtualization hypervisor pieces built into Fusion 12 don't work on Apple Silicon.
However I suspect your specific use case for managing ESXi and accessing the ESXi VMs via console don't depend on the hypervisor bits in Fusion 12 that don't work on Apple Silicon.
That all being said, give the Tech Preview release (which is built to run on Apple Silicon) a try and see if it works for you.