It was forced through by breaking the rules of the process and overruling the committee that should have made that decision. Many old-school Debian maintainers quit in disgust at that point, so if subsequent votes have been in systemd's favour then that's probably why.

Some source would be interesting, because it is just blind words otherwise. Also, Arch and several other distros made the choice independently. I am fairly sure Red Hat is not some evil entity kidnapping the families of maintainers making them switch to systemd..

No rules were broken.[0]

[0] https://www.debian.org/vote/2019/vote_002