This seems like a consequence of the rise of cloud computing. My experience is probably biased by the fact that I've been working in the Seattle area for most

This seems like a consequence of the rise of cloud computing. My experience is probably biased by the fact that I've been working in the Seattle area for most of the last decade. I've worked with and hired excellent engineers with Linux backgrounds and also Windows backgrounds. Elsewhere it may be harder to find top Windows devs. In the '90s, developers built their own Linux desktops and servers because there wasn't any IT infrastructure capable of supporting us. After the dot com crash and the nearly simultaneous death of big-iron Unix, Linux IT support started to become a thing. Medium and large companies staffed up on Linux sysadmins and support staff, so it was possible for devs to just code and remain fairly ignorant of the underlying OS - or at least confine their knowledge to the theoretical domain. Now that you can just spin up server resources in the cloud, I can see devs with Linux experience having an edge over those without.