Most of the software needed to provide a useful desktop Linux never runs on servers, so we cannot conclude that it is safe to use desktop Linux just because Linux is a popular server OS.

Also, at organizations like Google with a good reputation for security, most of the Linux installs are connected to internal networks that are quite difficult to break into from the open internet. The Linux installs at Google that are connected directly to the open internet are very carefully configured to minimize attack surface.

And Google has an internal team of Linux kernel maintainers that do not share most of their work outside Google.

Not any more. Not with a new LPE being discovered every week. Containers are dead, user accounts are dead, VMs are on shaky ground. We're currently getting the same level of security from Linux that we got from Windows ME.