Why is Ruby more suitable for Rails than Python?
All of this is TOTALLY "IMHO"
In Ruby there is ONE web-application framework, so it is the only framework that is advertised for that language.
Python has had several since inception, just to name a few: Zope, Twisted, Django, TurboGears (it itself a mix of other framework components), Pylons (a kinda-clone of the Rails framework), and so on. None of them are python-community-wide supported as "THE one to use" so all the "groundswell" is spread over several projects.
Rails has the community size solely, or at least in the vast majority, because of Rails.
Both Python and Ruby are perfectly capable of doing the job as a web applications framework. Use the one YOU (and your potential development team) like and can align on.
Python and Ruby are usually considered to be close cousins (though with quite different historical baggage) with similar expressiveness and power. But some have argued that the immense success of the Rails framework really has a great deal to do with the language it is built on: Ruby itself. So why would Ruby be more suitable for such a framework than Python?