> I’d say “neither”. CentOS would have fail had Redhat not taken over.
While it's possible that CentOS would have failed (I'm not sure slow initial releases actually indicate that), it also wasn't the only popular clone of RHEL in popular use. Scientific Linux (developed by FermiLab) was also popular and in fairly wide use. I doubt Red Hat would have made the change to CentOS that spurred all this if Scientific Linux hadn't decided not to continue and just use CentOS instead in 2019, because instead of a "crap, we have to start a new distro to provide what CentOS did" movement there would have been a much quicker and easier mass exodus to Scientific Linux.
The Scientific Linux team decided to not make a Scientific Linux 8, and instead switch over to CentOS 8[0]. Note this was announced prior to the announcement about CentOS 8 going away.
While it's possible that CentOS would have failed (I'm not sure slow initial releases actually indicate that), it also wasn't the only popular clone of RHEL in popular use. Scientific Linux (developed by FermiLab) was also popular and in fairly wide use. I doubt Red Hat would have made the change to CentOS that spurred all this if Scientific Linux hadn't decided not to continue and just use CentOS instead in 2019, because instead of a "crap, we have to start a new distro to provide what CentOS did" movement there would have been a much quicker and easier mass exodus to Scientific Linux.