Good progress of Linux gaming probably contributed to this.
The biggest driver of adoption is simply more computers sold with Linux pre-installed. Very small fraction of users ever installs an OS.
It is possible, and that's great, but boy Dell et al do obfuscate the choice on their sites. You have to know the machine exists, need to know the generation, the year, etc.
It's almost as if they don't want people to buy these machines.