The blunt reason is that they don't give a fuck anymore.
The deeper reason is that they know whatever it is they do, it will come back to them anyway and they will somehow be at fault.
For example, my mom nagged at me once for the loud volume from my computer.
I hence shut the door.
One day, she texted me asking why my door was always closed. It made her feel lonely and that I was acting as if I was a tenant in the household.
Fuck me right?
How dare I... carry out the main function of a door?
How dare I... not read my mom's mind that changes at every whim?
How dare I... even try to create a solution to a problem when the solution would eventually become the new problem?
Hence this is why intelligent people eventually behave badly: Because anything we do is wrong.
So we liberate ourselves and just do whatever we want even if it will offend others.
"But come on Alden! Be reasonable! You can simply adapt along the way and appease others. It's not that hard."
No, you don't get it. The cycle will always exist. It will STILL eventually be our fault as some new, magical grievance over something minute and stupid will show itself.
How do you break this cycle? You can't.
So you might as well do whatever the fuck you want without stressing out over someone else's feelings.