I remember a show of hands on distro use at a linux conference in the mid 2000s and just about everyone used Debian. I think we were all suprised. I suspect that would be different today with Ubuntu variants, Arch, Fedora but I doubt the handful of actual Red Hat users has changed. They always presented themselves as a much bigger distro than they ever were and their advertising and media coverage gave a very skewed impression.

I would see people using Centos and ask why and it was because they were in IT, but not grass roots linux users, and they thought Red Hat was the major Linux distro because of all the publicity they bought and the certifications. Red Hat's importance was that their relatively small number of enterprise customers brought in real revenue which funded full time developers and was a huge benefit to Linux. But for average Linux users they were and remain a bit of a side show.