\* and DHH happens to make good decisions frequently enough.
For every successful BDFL example, history is littered with a hundred dead languages and frameworks designed by a single visionary leader who made the wrong decisions.
E.g. there's the namesakes for Rails and Ruby, i.e. Grails and Groovy. Virtually no-one's upgraded to Grails version 3 since it came out 3 yrs ago, or started new projects in Grails version 2. The Grails 2 plugin ecosystem is as good as dead. It only has its "single visionary leader" listed for the 3 contact persons (owner, admin, tech) in the grails.org DNS registration.
As for Apache Groovy, it's hanging on as the build language for Gradle and Android Studio, but doesn't seem to have any other significant use besides its original use case of glue code and testing harnesses. Groovy's problem is its creator, who had successfully added closure functionality to a clone of Beanshell, left the project after 3 yrs and the "despot" at Codehaus who subsequently claimed the title Project Manager was someone who didn't have the aptitude for many programming tasks.
Fortunately Perl5 still does the Pumpking thing which is effectively a rotating BDFL.
I would say that this hasn't been the case for the past 10 years at least. Patrick Michaud has been Perl 6 pumpking since then, to make room for Jonathan Worthington about 2 years ago. Hardly a revolving door and hardly clowns.
(It's not all the pumpkings' fault, either. I think Parrot would still have been doomed if its leadership were constantly flawless, just because it was designed before Perl 6's object system was.)