I was surprised too. I don't think it can simply be explained away with fans losing interest in Bradley over the Pac decision. This was a well known name in a fight of the year and it only even peaked at 1.4 million? These are Maidana numbers right here.
This time I'm especially wary of the source since it was released by a twitter page I'm not familiar with who said "as per HBO's press release" when HBO haven't actually made any press release. However, the fact that there hasn't been a press release is as good a sign as any too in itself.
I've always wondered if there are guys out there who wait for HBO to stay silent just so they can jump in saying they have a source who said such and such. It's like Front Row Brian and his saw off shotgun reporting, make enough claims citing your "source" and one is about to land. Get it wrong - just shrug your shoulders and say oh well that's the game.