Put a large carnivore in a small cage and it will go mad.
An animal designed to wander, hunt, fight, compete for mating rights and die young will go mad placed in a secure evironment with low risks, minimal conflict, monogamy and the chance to live to a ripe old age. Not built for that.
We need to reintroduce risk. We need to provide controlled opportunities for conflict. We need adventure, dangerous jobs and long expeditions. Risky behaviour among men is to be encouraged. We need to stop wasting billions on sending remote probes to other planets and start sending men instead.
We've forgotten that men are expendable, made to be put into dangerous situations where only the best and smartest survive to breed. But our genes haven't, and when society doesn't provide an outlet for these instincts, men will make one.