I'm not sure why it's so hard for anyone to find this on their own. OpenShift forced users to use CRI-O and RHEL removed Docker as part of the Yum repository.

Plenty of references to this: https://crunchtools.com/docker-support/

Even though, at the time, CRI-O was a much worse option. Yes, Red Hat plays competitive lockout games all day long. This is just a singular example.