The Manchester bomber is a child of immigrants. Children of immigrants turn into a high-risk group in terms of anxiety, depression, alienation and anger if the parents resist integration or refuse to acknowledge that any emigration is a traumatic rupture that requires compensatory mechanisms. If the parents choose not to compensate, children will have to do it in a much greater degree.
When such children end up stuck between two cultures, the private and the public, unable fully to move into one or the other and lacking the intellectual sophistication to turn this situation to their benefit, they might act in destructive ways. The nature of the destruction is, of course, mediated by gender and culture. Some people will thwart their own lives, others will visit devastation on their immigrant community, and there will be some who will go to the extremes of the Manchester terrorist.
None of this is aimed at justifying the act of terror, of course. Everybody has shit to deal with, and it’s everybody’s choice how to do that.