There isn't one answer to those questions
I think we need to try and understand more the pull for young Muslim men towards groups like ISIS. Is it the desire for to have power, driven by anger and hatred towards the west,
Many who are joining are from countries that have very high unemployment rates, many highly educated, countries that are torn apart by the Arab Spring revolution and life hasn't improved
Maybe ISIS provides a structure and some form of security while also being able to channel their anger and hatred
That of course would not be the reasoning for all that are joining some obviously have the desire to spread an ideology that is based on Islam that is non progressive and treats women with no respect and non Muslims as the enemy
And yes as one French minister said we have to accept that we are at war and we are going to face more of these attacks but we have to fight back and that I beleive is with a collective force and try and halt the spread of these extreme forms of Islam and there funding