I do remember a well-timed post on reddit/r/programming about Nimrod (as it was called back then), shortly after Go's release. It contained a lot of "Go is disappointing (to put it mildly), this looks so much better"-comments about the language. The backlash against Go was pretty huge.
I don't remember the guy behind Nim doing much trash-talking, which probably helped as well, especially in the long run.
The problem of Go is the hypocrisy of its community when it comes to the expression problem. Obviously Go isn't expressive at all. Which make it verbose when one tries to write abstractions with it.
A lot of devs just want a fast,type safe,memory safe language,that doesn't need a hungry VM to run but is expressive enough so "scripters" feel at home. Why is it so hard to get a language that does that? IDK .
I don't remember the guy behind Nim doing much trash-talking, which probably helped as well, especially in the long run.
EDIT: fixed derailed sentence.