1) systemd was not pushed at GNOME; the GNOME dependency was the leverage used to push systemd at distributions. This let the systemd cabal look innocent with GNOME getting the blame for any compatibility issues. This is a very common political tactic that is popular because it gives plausible deniability and usually requires more than a sound-bite to refute. Surely you've seen it before.

2) I read debate on the Debian tech-ctte and surrounding discussion in realtime when it happened. GNOME compatibility was a key concern, and while the idea of dropping GNOME was briefly considered, concerns about supporting GNOME ended up having significant sway and a big reason - though not the only reason - why systemd won the vote.

This would normally be a purely technical decision, but in this case the GNOME->systemd dependence only exists because Lennart Poettering created it.