I think they answered the question for you:
"they failed to master Ruby"
I think with Ruby and RoR you really do have to understand what you
are doing. I'm not sure of the complexity of the project, but I would
hate to think that a team would adopt a new technology without doing
some sort of pilot project first to understand the technology they are
using. I know from my experience, the second project I was a lot
different from my first self-initiated one.
One of the strengths of RoR is the "convention over configuration" so
it allows to get started quickly with out having to jump through hopes
to do simple things. But it won't design a good domain model for you
etc. The technology could be used as an escape goat too. A lot easier
to assign blame to a technology that cannot answer back
Here's a list of high profile applications running RoR: