I suspect his silly and fun-sounding "kinda drunk" brand voice was what set them apart from all the other boring dev tools in the space.
https://quoteinvestigator.com/2016/09/21/write-drunk/
Looks like it was Peter de Vries, but the hallmark of a good quip is shambolic attribution.
Personally, I'm in the audience that that style works well on, but I can also see how it might be harder for someone to follow that style. e.g. if English isn't their native language. Similarly, I imagine that style is also much harder to localize (not just translate).
I think both techniques are great and I don't think they're mutually exclusive. That is, you can still inject flavor and style within the confines of a technical style guide. You just do so in a way that's less... flamboyant?
Four and half years later, I'm still employed as a professional Go programmer.
Thanks, Brian!