That's a somewhat different situation: they take different levels of purity test on licensing (not to mention falling under different legal considerations depending on where the developers reside) but adding or removing Mongo has little ripple effect for anyone who doesn't use it. If they don't ship it, the people who were using it will switch to Mongo's main YUM repo and nobody else will notice.
In contrast, changing the init system affects every package which runs a daemon and systemd does more than most of the alternatives so supporting multiple init systems is a substantial amount of extra work which is unlikely to attract corresponding volunteer assistance or result in any user-visible benefits.
Well, yes, you're very much right on that regard, and as others mentioned, the 'official installation instructions' were always using Mongo's official repo, so it's a different case.
But I still feel that Red Hat has pull with the Linux industry, and others might make their decisions based on "what's RHEL up to".
> others might make their decisions based on "what's RHEL up to".
Looking at systemd from one angle might lead one to think that, but I viewed it from a different angle. It's obvious from the different distros that have replaced the SysVinit system that they were looking for something it wasn't providing. Systemd apparently provided enough of those capabilities to be viewed favorably by some distros, or they looked at the extra capabilities and decided that even if they didn't like aspects of it, it was important to support them to compete.
I'm sure Redhat did evangelize it, but I doubt it went along the lines of "hey, we're Redhat, you want to be doing what we're doing." Instead I think it was more like "Hey, we built this cool new thing. Let me tell you about all the new things it has to offer, and how it solves these problems you've had."
… and we have $x worth of development time solving problems which you have with your current init system. It's not like distributions have an unlimited pot of money, and this isn't something which really sets them apart from other distributions. Ubuntu had been developing their own but switched to systemd years ago and that's generally been either unnoticeable or noticed only in that you don't have to spend time working around Upstart limitations. It's hard to make the case that they'd have been better off spending that money duplicating effort for something which will have almost no impact.
In contrast, changing the init system affects every package which runs a daemon and systemd does more than most of the alternatives so supporting multiple init systems is a substantial amount of extra work which is unlikely to attract corresponding volunteer assistance or result in any user-visible benefits.