I think it is directly related to Oracle, as Oracle literally is just RHEL, with cheaper support (which they can afford to do, because their development costs are tiny compared to RHEL, if they just copy the code every release).
The others I’ve seen used it as a base, but aren’t really competing in the same way. CentOS also wasn’t providing commercial support… Either is Fedora. Commercial / Enterprise support is how Redhat makes money. And that’s how Oracle is planning to make money too
Also, what is wrong with IBM? I don’t recall them doing anything bad for open source. they fought SCO, and have contributed a lot to the community