Makes all the sense in the world if you understand it was a suicide attack from the getgo....just a slo-motion one compared to 911 or many of the others.
This is Islam - the terrorist wing. It's how they operate.
According to islam there are two parts of the world — Dar ul Harb where disbelievers live and Dar ul Islam where Moslems live. It is the Islamic tenet of faith that Darul Harb should be a place of strife and war, until the peace of Islam comes. So your hometown, your neighborhood will become a place of strife and terror until you embrace Islam. THAT is what these jihadis want, nothing else. Islam is not logical, not moral, nothing - it is the worship of Satan/Allah, nothing more.