That’s literally all there is to it. Even in the olden days it was a well known fact that a generation of young men without (economic, social, romantic) perspective is a generation who will radicalize to either side. If the system isn’t working for them they will seek to change the system.
If politicians were serious about curbing extremism they would make sure everyone simply lives a decent standard of living, with prospects for their future.
Its also why I believe most modern governments try REALLY hard not to go to war. Not because of the death and destruction but because they dont want a combat trained populace.
Also because shared adversity unites, the differences between people get really unimportant when they are trying to keep each other alive in combat.
The idea of a significant percentage of “us” coming back and being united and trained well enough to actually threaten the system scares the piss out of them.