All the changes to gnome, which depended 100% upon systemd at the time, were pushed by redhat, gnome contributers.
This one of the biggest reasons given, for getting systemd into debian at the time.
When systemd was being pushed origionally, fast boot times, predictable names, and a few other things were big reasons. Yet debian already had parallel init booting, and already had predictable interface names.
Systemd has done almost nothing for debian, and has many drawbacks, as you say.
Systemd was a redhat solution, to redhat issues, and redhat used its power in the community to force it through.
There were a lot of outright lies, politics, and more at implementation time. And you're right, part of it was redhat wanting to force systemd, and no other.