Interest in the freakshow
doesn't necessarily equate with interest in the music, per se.
Sure there are a lot of teenie-boppers out there who think that Spears' music (and I use that word in it's loosest sense) is cool. But a lot of this activity is based on the typical bread-and-circuses interest in a freak of nature. A lot of folks are just curious as to how her new music sounds, perhaps wondering if it's as bad as the MTV show seemed to indicate.
I wouldn't count the initial release of the first new song from the album as a "comeback" quite yet. Let's see where the numbers are in, say, 30 days when the bizzaro factor has worn off.