Perl6 was a much greater mess than Python3.
I'm more surprised that Ruby didn't do better.
As you say,
> Network effects did the rest.
In an alternate set of universes, Ruby has Python's current position, and you are wondering why Python didn't take off. (But I suspect Ruby evolved fairly differently in those cases.) The universes where both are popular are much rarer.
Perl6 was a much greater mess than Python3.
I'm more surprised that Ruby didn't do better.