However I don't understand why Django did not gain as much as RoR did
Two reasons.
First, unlike Python, Ruby didn't have any viable web framework in 2004, so it was easy to attract Ruby developers.
Second, and more importantly, David is much better marketer than Adrian. He poked the J2EE hornet's nest and evangelized the hell out of Rails for the first year and really got the snowball rolling.
and also because python programmers are confident of their language and ecosystem not to resort to gimmicks like the "F* You" slides.
It could have ended badly for Rails except that lot of Java developers ended up tasting the heady mix of dynamic languages and web 2.0 via Rails thanks to Java gurus like Martin Fowler. And coming from the staid world of Java, a colourful character and opinionated framework was hip and happening.
Meanwhile, pythoneers did what they do best, keep producing good code and documentation. This is a recurring theme across many areas where python is good at not just web frameworks.
Python does not nurture over the top behaviour (I notice that neither does Ruby.. Rails is another matter).
and also because python programmers are confident of their language and ecosystem not to resort to gimmicks
But not confident enough to be just a little bitter about Rails' success?
Seriously, if you think DHH is an asshole then say so. Maybe you would never sink to his level to promote your project. Fine. But jumping to the conclusion that he's not confident of his language is just rationalization. The ugly truth is that brilliant tech is ignored every day because someone didn't know how to market it.
Two reasons.
First, unlike Python, Ruby didn't have any viable web framework in 2004, so it was easy to attract Ruby developers.
Second, and more importantly, David is much better marketer than Adrian. He poked the J2EE hornet's nest and evangelized the hell out of Rails for the first year and really got the snowball rolling.