The simple fact that more and more work is less and less physical, alongside the collapse of mandatory physicality for social events. A soldier of the era grew up running around with friends or reading books, and you couldn't exactly order a years worth of paperbacks on amazon back then. There was no realistic alternative to going out and doing for 99% of the population, and when you're out and doing, you're not grazing on snacks or lazing. That alone accounts for a lot of it.
Kids these days are growing up actively discouraged from being outside - the social norm is video games with the boys, not wandering around. Set that as a habit when yer single digit years old and its hard to break.
imo, it's less about a very complicated series of events and more, in a phrase, more western people are becoming pussies. hard times create strong men etc. children in the west for a long time have been so well fed and safe, along with propaganda/directed education, that their emotional tolerance, empathy etc is wired wrong. during a major downturn event, like the great depression, ww1-2, if someone was breaking down into tears over palestine or ukraine or some shit, they'd be laughed at or bullied or worse, and that would carry on for some time. ww2 vets were not crying over children in africa, or at least metaphorically, their tolerance etc would be higher and everything would be about the shit in front of them first, then "oh yeah that sucks" normal responses about anywhere else, but if someone said "meh that shit doesn't matter" they'd say "yeah you're right, need to worry about feeding my family", instead of various "you're evil, literally satan" etc.
even then, another war or event wouldn't be enough, empathy has bellcurved into retardation and/or evil, letting black men out from assault+ on no bail literally 10+ times, protecting illegals, hell, rioting with them waving foreign flags, censoring the amount of black crimes, letting drug addicts or worse roam the streets, being encouraged to give them money, nobody actively removing them so they just become living toll booths sitting beside every red light, or you get pushy ones like "yo you got any change? really none? can i wash yo windshield? you ain't gonna give me work man?", if they're not violent and/or insane. there's a narrative where all homeless people, if given a free house and minimum wage, suddenly will become "normal", weird racism among the left where black people can't be held accountable and should be always treated with kid gloves and let out free because slavery. rape, murder of your family/friends/ neighbors, 4k footage of a black man stabbing a white woman then saying "i got that white bitch" is just a fact of life (but guns are pure evil and are never)
then you have the entire welfare state, where if a cataclysm ever happened and gibsmedat stopped, then in a unrealistic utopia where politards shut the fuck up and planted shit and retained common law and dealt with it, you'd still have a divided nation with a very sizable zombie horde that would go batshit and are already threatening to from an extended shutdown. tons of said people on gibs me dats also are bored or think they're changing the planet by dumb shit so become roaming protesters looking up the next big meeting while getting free checks because they doctor shopped enough/knew the right people/got lucky to get perma disability off a sprain or some shit.
imo realistically the only way to ever "fix" any of it would be very rough and would involve true, actual, non wikipedia definition fascism the likes not before seen, of essentially mobilizing the full army with people that will do dirty shit, firing those that won't, doing very major changes that won't be taken well, stomping the boot to dissenters, and then after a very bad period becoming something like china itself. too many people are too stupid and too easily swayed by emotion, so the only option is to just eternally be locked to them or to have some form of dictator appear that removes or deals with them and then forces the general populace into lockstep, but that wouldn't really be able to ever happen because even someone like trump is considered hitler, and everyone in government is 90+ and just wants more money, and would sell the entire country and build migrant rape cities if they got the right offer, because fuck it, they can just move somewhere else and buy a megamansion with a security detail and ass wiper.