Redhat gains at least a few things...

- Maintaining X requires a lot of time, expertise and cost, it's a hard codebase to work with, deprecating X saves them money

- Wayland is simpler and achieves greater security by eliminating features of the desktop that most users value, but perhaps Redhat's clients in security-conscious fields like healthcare, finance and government are willing to live without

So I suspect it comes down to saving money and delivering something they have more control of which is more tailored to their most lucrative enterprise scenarios; whereas X is an old mess of cranky unix guys and their belligerent libre cruft.

There are some parallels to systemd I guess, in that its design rejected the Unix philosophy, and this was a source of concern for a lot of people. Moreover at the time systemd was under development, my impression of Poettering was that he was as incompetent as he was misguided and belligerent - he was also advocating for abandoning POSIX compatibility, and PulseAudio was the glitchiest shit on my desktop back then. But in the end systemd simply appeared on my computer one day and nothing got worse, and that is the ultimate standard. If they forced wayland on me tomorrow something on my machine would break (this is the main point of the OP), and they've had almost 20 years to fix that but it may arguably never get fixed due to Wayland's design. So Wayland can go the way of the dodo as far as I'm concerned.

The statements "Rejecting the unix philosophy by being a huge monolith which does too many things", and "systemd is actually 69 different binaries, only one of which runs as pid 1" are mutually exclusive. The latter is provably true, so the former must not be.