Of course they're trying to take Rock Band down with them and not admit to their own culpability. They're Activision.
Here's a quote from a CNET story that I'm sure Activision won't acknowledge:
"It doesn't surprise me," said Amanda Caparoon, a Seattle bartender and music gaming fan, when told Activision was burying the brand. "There's cooler stuff now, like Rock Band. And dance-based games are where it's at now."