Premature explosion?
An article posted to the Kefaya movement Web site claims to have a picture of the bomber. The accompanying article reports that the bomb probably went off prematurely. If true that should answer all the questions as to why he'd have set it off in the Muski, a somewhat less tourist oriented area.
A security source said that the bomb exploded while attached to the terrorists body, mutilating him before he could detonate it.
First signs of the investigation of the Cairo Bazaar bomb are that the bomb was secured to the body of the bomber and went off prematurely.