Actually Sergey, it can be none of the above. One of the killers is English. He was born here. He was raised as a Christian but converted of his own volition. The closest would be a consequence of multiculturalism but I dont believe that for a moment as extremist Islam is a very rare thing in UK no matter what some mouth breathers would have you think.
You have to be a sick ****** to try and cut someones head off, unless Islam makes you into a sick ****** I would suggest this guy was wired wrong and I would be more than happy to be ROP'd for suggesting its more likely his African background than his choice of religion.
Social exclusion springs to mind to be honest. In this case individual exclusion which could be due to his background, attitude, social skills, education (or lack of) and unrealistic expectations of jobs/future.
His conversion to Islam indicates (to me at least) that he was trying to move away from his own background and forge a new social identity. When it didn't improve his future prospects he could have been prone to radicalise.
Anyway, loads of speculation....... We'll have to wait and see what he says about it all himself.
There's an element of our immigrant population whose model of existence is to re-create their country of origin but with UK living standards. There is also an element of our political class which is happy to let them do this for party advantage.
Where there is a real desire to integrate, the system works reasonably well. Where there isn't, the powers that be have been consistently gutless in pandering to certain minorities and their attitudes, refusing to challenge them, and constantly using this country's institutions to stifle debate and intimidate anyone who suggests that there might be an issue.
The biggest victims of this last policy have been public agencies such as the police, and moderate members of immigrant communities who have found themselves marginalised and ignored whilst the loonies have been granted political access and media airtime.