"The average age of a Radio 1 listener is 32, with Grimshaw drafted in by controller Ben Cooper as part of a strategic move make the station more appealing to its target audience of 15- to 29-year-olds." - from the Guardian article.
The original tactic hasn't worked clearly. To be a million down on Moyles' average isn't disastrous but the show hasn't improved that much to only draw in 100,000. Sounds like the BBC are clutching at straws at the moment. We may see that 5.9 million figure drop like a stone between Aug - Oct because Q3 is normally the quieter of the 4 quarters (holidays etc) if the show in general doesn't improve.
Having listened to some of Grimmy's show recently; it seems like all the initial flag-waving of this "less-zoo format", more music crap has gone out the window. We definitely know Grimshaw is not in control of the show that's for sure.