People go to the US with the expectation to work for a living. People come to Germany with the expectation to land in a social safety net. People (2nd or 3rd degeneration immigrants) grow up in France with a similar safety net. They get money, but many fail at school, don't work and get no respect. Also many extremists in Germany and France have a criminal career before becoming violent or radicalize in prisons.
While failing at school, jobs is a common cv for this generation of terrorists, the 9/11 attackers were from well off families. We all know of course what the one common denominator is.