What services are they offering that makes them attractive to corporations?
Mark Monitor will apply a lot more filtering to complaints.
Ironically this is allegedly what happened in this case, a complaint about the domain got it taken offline.
It's like, as I'm sure I'm paraphrasing from something I read God alone knows how many years ago, if your publicist lets you walk into a press event with a giant blob of snot hanging out of your nose. There surely is a reason why that error occurred, and it probably is at least a pretty good reason. But no one is very surprised to see the intro invite from your new publicist.
It isn't a relationship you blow up on a whim, but Zoom that can't route call traffic is Zoom that's not generating revenue, and while the reputational impact is negligible if it happens once, it had really better happen only once. Zoom is the incumbent; no one remembers they were revolutionary once, now everyone only notices the parts they don't like. (Being a skilled but politically naïve sysadmin is much the same.)
Basically, this is why Ma Bell - which had about the only stronger possible "uptime" expectation, in that no one uses Zoom for 911 - was so uptight you couldn't even plug in a modem until about five minutes before divestiture, and specified everything down to the number of turns in the splices their technicians made. There was a fad among programmers, when I was a child, to consider such practices stodgy.
What MarkMonitor can provide is things like facilitating RegistryLock, which makes it even harder for changes to be made. And account reps that know what's going on. I hate working with account reps, but if they're knowledgable and easy to work with, it's ok.
They do some trademark monitoring (thus the name), if you want to get your own related app taken down from Google Play :p (I'm not bitter, it was amusing). And presence services if you need to hold a domain in a weird location that wants a presence, they can probably arrange it, which is handy at times.
I'd love to know more details on this incident, MarkMonitor had a bulletproof reputation as a registrar that won't fuck up. Godaddy doesn't, but then I didn't realize they had taken over the contract for .us
(As opposed to a DNS server, including root servers - and even then DNS has provisions for downtime, not to mention redundancy in configurations)