I don't think we've heard the full story about Salman Abedie yet, so I'm not going to jump to conclusions. Something you've missed out of his life story Terri is that his parents apparently went back to Libya in 2011, when he was 16. There are contradictory reports about his father's influence. Didsbury mosque is also claiming that he was banned for swearing at an imam, who spoke against extremism.
Nevertheless, a pattern is emerging. Newly arrived immigrants have made a choice and usually make efforts to integrate, knowing full well the problems they are likely to face in a new country. Second generation immigrants (which many who have committed atrocities in Europe are), born in a new country, didn't make a choice to become part of a minority group.
Not only do immigrants suffer racism, but they often have difficult relationships with their parents and their "traditional" church leaders, who might want to impose rules which are incompatible with a Western lifestyle. Many teenagers, even from more stable backgrounds, drift into gangs and/or take drugs without life seeming to have any meaning. Jihadist recruiters exploit that insecurity.
There is no easy answer, but I'm convinced it needs to be based more on psychology than on bombs. Even if Syria, Iraq and Libya were completely destroyed, the movement has already spread like a cancer.
Some Muslims have been speaking up for years, but it seems few have been listening. After all, many more Muslims have been killed by extremists than anybody else. Muslims don't make up a homogenous group. A Saudi, for example, will have been brought up with a very different culture from an Algerian. I don't feel that, as a group, Muslims should feel responsible, although I also feel that any solution must come from Muslims themselves. I don't think the West can act in a colonial fashion and impose a solution, although equally I do think we have a right to impose our own laws and expect all citizens to adhere to them.