> systemd has been adopted by many different distros, however this is not because of "top down" pressure (From who, Red Hat? Most distros don't answer to Red Hat), and most of them don't have a (B)DFL who could have imposed that decision on them.
Often it was a "matter of fact" thing. If the ecosystem under the distro changes to use systemd distros will follow. There might be more advantages to it, but it being required to run Gnome 3 without additional effort, and in general other servies starting to rely on it, make the decision pro systemd the easy one for distro maintainers. You can see that point being made in the debian discussion on the issue.
Till they hit the showstopper bugs and can't solve them.
sysvinit is short enough to be trivially maintainable. If you're just using it as a shim to load a framework on top of it, you can ditch even more of it cutting it down to around 500LOC (see openrc-init). So that's not a large enough part of "the ecosystem under the distro".
Debian maintained their own init-scripts framework (and still does, for kFreeBSD and other kernels), so that certainly didn't move out from under them.
Arch Linux maintained their own initscripts framework, so that wasn't moving out from under them.
I suppose there is a case to be made that distros were pushed to systemd by Gnome 3's reliance on systemd-logind's D-Bus API.
Often it was a "matter of fact" thing. If the ecosystem under the distro changes to use systemd distros will follow. There might be more advantages to it, but it being required to run Gnome 3 without additional effort, and in general other servies starting to rely on it, make the decision pro systemd the easy one for distro maintainers. You can see that point being made in the debian discussion on the issue.
Till they hit the showstopper bugs and can't solve them.