The Manchester Bombing makes no sense to me.
I can understand people bombing a government facility. It represents public policies that make that person(s) feel oppressed and they are fighting "the power". I see how they get there.
I can understand school shooters and employees who "go postal". They feel they have been disrespected by the people there and they've had enough. I see how they get there.
I can understand how a group bombs a transportation system to cripple an area - generally again to get back at "the authorities" who have perpetrated some kind of injustice or oppression in their minds. I see how they get there.
I can understand (after watching enough Criminal Minds) how serial killers pick victims that fit some dark tortured spot in their soul. I see how they get there.
But I don't see how blowing yourself up at a concert hall full of teenage groupies accomplishes anything. I see nothing that is accomplished or any message conveyed that makes sense. I don't see how you get there.