I can't imagine what the bomber hoped to achieve by this act.
Support for Isis? Persuade everyone that we all need Shariah Law? Perhaps not even a Muslim at all.
A personal statement of political disagreement? Was he/she just a loner with a grudge? A nerd who researched online about bomb manufacture and wanted to 'try it out'?
There isn't one single reason I can come up with why anyone sane would do this.
My husband wondered if there had been security checks on bags etc at the venue. I suppose the numbers of people at the concert were just too great to search everyone thoroughly.
I feel such sorrow for all involved. Nowhere is safe now.