I wonder if DC thinks what they did to Harley in the new 52 made her blow up. The only thing I can see that sorta contributed to her mainstream exposure is them officially making her a member of the suicide squad(I think she did one mission post crisis) which has kinda been carried over in Arrow and the animated movies.

Still Harley's book isn't really about anything but her going on wacky adventures that have nothing to do with anything in the new 52. Maybe that's the point but then again that doesn't work with every character