I was talking with a Microsoft employee that works in azure. Something like 60% of their VMs
are Linux.
Not everyone who uses Azure is a "Microsoft shop", in terms of programming tech stack. Plenty of people use Azure as a cross-cloud redundancy play, or because they do business with Amazon competitors that refuse to have their data on AWS.
It's the reverse in AWS, they have a bit more Windows market share than Linux. And he also backed up your statement.
His take (which was just his speculation) was that the virtualization stacks ran those OS's more efficiently. HyperV with Linux VM's and KVM with Windows VM's. I have no idea if that's true or not.