It isn't surprising to me. It's stated elsewhere they tried 4 difference version of Go, up through 1.10 apparently, and had performance problems with all of them. At some point you can't suffer garbage collector nonsense anymore and since they'd already employed Rust on other services they tried it here.
It worked on the first try.
That's not surprising either.
What would be surprising is if any of these "but version such and such is Waaay better and they should just use that" actually panned out. The best case would be that the issue just manifests as some other garbage collector related performance problem. That's the deal you sign up for when you saddle yourself with a garbage collector.
