Just like Windows 11 is different from Windows 98 (98 doesn't mean it's newer).
They went through a rebranding from RedHat Linux to RedHat Enterprise Linux over a decade ago but after or during the SCO nonsense. Early versions of RedHat's Linux were just called RedHat Linux because at the time it was just like any other Linux distro or starting from those early hobbyist roots. RHEL was meant to be stable and have commercial add ons for big companies.
What could be thought of as Red Hat Linux today is the Fedora distro (which it was spun off into), which is upstream, more frequently released or up to date (and thus less stable), and targeted at the hobbyist or enthusiast user, which I'm one of the weird people that still uses it. Once something useful goes through its paces on Fedora, it'll eventually get integrated into RHEL where reliability is of higher value than the latest features.
I started on RH 5.2 myself, in '99, and literally got it on disc for $40 at BestBuy. I also lived near RedHat's offices (in Durham, NC) at the time and got to visit them once with coworker friends. Exciting time, I was very young, and wish I knew enough to buy stock during its IPO at the time.
At the time it was just “red hat linux” while today it is “red hat enterprise linux”.
The split (and the counter reset) was made to mark the split between a regular distro (fedora core, at the time) and an enterprise-oriented distro (red hat enterprise linux).
There was a distro called Red Hat, which more-or-less mutated into Fedora, which is and has always been a different distro from Red Hat Enterprise Linux.
