( 14 Mar 2012 , if the sympa archive make your life difficult ).
But the main reason is simple.
"people are free to do what they want". A group of volunteer cannot do much besides doing the work itself. So if no one stepped to participate, the project can just state the obvious. There is no CTO to say "you will work on this as part as your job".
And while it is quite exciting to be part as something new for Mandriva people ( as some have invested lots of time in this ), it seems obvious to me that this is less exciting for people who did it 2 years ago. Would have Mageia turned out to be a fiasco, yeah, I am sure people would have participated and tried again ( Mageia was not the first attempt to have a community project, but it is so far the most successful ). But it is working fine, so no one feel the urge to start again almost from scratch.
And I am sure than with a more concrete proposal ( because that's always the main point, everybody is ok to collaborate, but what does that mean in practice is much more complex ), things could change.