In reality, one only need look at the many different package management attempts to see how Python failed at living up to its own aspirations. If more evidence is needed, take a look at the packages themselves, and you'll see lots and lots of duplication of effort and incompatible ways of doing the same thing.
Perl's CPAN was widely reviled by Python fans for having lots of cruft collected over the decades, and not knowing if the package one uses is the "right way to do it", and Python's "one way to do it" approach was supposed to be a solution to that. Well, it didn't work out that way. There are now tons of crufty Python packages, with similar quality control issues.
I think this is merely a result of a language becoming popular and having a robust community of developers. Developers like to re-implement things and write them from scratch, whether just for their own education or amusement, or for geek cred, or to look good on a resume, or because they finally want to write it "the right way" (of which everyone seems to have a different opinion on). Then they abandon packages when they're no longer interested or when something else takes priority. Happens all the time.
If Go hasn't had something like this happen to it yet, it could be because of some visionary design that somehow avoided these issues, or it could be that it's just not as old and popular yet.