Redhat was involved because they heavily maintain some of the upstream packages that put in a hard systemd/logind requirement (GNOME), thus forcing Debian into the uncomfortable position of taking on a large compatibility project, when upstream could have instead taken small patches to continue to maintain compatibility with non-systemd systems.

Which packages had a hard systemd/logind requirement upstream? As far as I understand it, GNOME still gets upstream patches from BSD developers and is still supported there. (Some Debian packages do have hard dependencies on systemd, but this is a downstream packaging issue)

I don't want to leave my hearsay uncited, but try here:

https://blogs.gnome.org/ovitters/2013/09/25/gnome-and-logind...

Slightly more recently:

https://digitizor.com/gnome-linux-only/

This was an eternity ago in internet time, and I'm not all up and up on BSD development, but maybe enough folks are keeping it going on BSD nowadays?

Interesting, I checked and the only upstream component of GNOME I could find that requires systemd and doesn't have a compile flag for it is gdm. This isn't required to start GNOME (you can use any other display manager) and FreeBSD/OpenBSD seem to be maintaining consolekit patches for it downstream. So I see why there is little incentive to fix this upstream. (On non-systemd Linux distros the focus has shifted to staying compatible with elogind, but that doesn't work on BSD)

But as a user I basically didn't have to care about the details and the "drama" aspects of that drama (I had the result to deal with of course)