My memory is that, at least outside of the web/RoR world, Ruby at no point as popular in the US as Python. Lets take, say 2005 as a point that Ruby was really gaining popularity due to Rails: at this point I was already seeing internal tools that previously would have been written in Perl being written in Python.
Python just seems to have maintained a certain momentum, and I'm not sure why, but if I had to guess:
1. The syntax is almost a dead-ringer for pseudo code. The first time I encountered Python, I fixed a bug in an open-source project having never seen Python before. I recall two different CS programs switched to Python from Scheme for exactly this reason.
2. It was designed to glue C together. Other languages were too (TCL and Lua; Perl primarily interfaced with the outside world in the same way shell does, with pipes).
3. A kitchen-sink approach to the standard library helped it a lot for the first 20 years of its existence. CPAN was sui-generis at the time for installing libraries, so the more you could do without relying on 3rd-party libraries, better off you were.