I see parallels to PHP initially taking off for web development instead of Python via mod_python. Paradoxically, it was so much fun to build your own web framework in Python that everyone did, so none got enough traction.

By the time Django finally broke through, PHP (with a good-enough mini-framework baked in) already dominated Python for web development, and the fragmentation of the Python world was arguably a contributing factor. Others adopted a third language because of a single mindshare-heavy framework, Rails.