Makes sense (in the twisted logic of these terrorists). They wanted to kill the Pope years ago in the Philippines at the same time as they blew up 10 jets. The plan was thwarted.
They wanted to blow up the WTC, tried once and tried again until they did it.
I think their obsession is the same. They want to kill the Pope still and do it as part of a double whammy. This time the Pope and US Embassy at the same time.