Does everyone just become their worst version when dating??

I swear I have dealt with this like ten fucking times already with friends, why does nobody talk about this.

So, I have had a normal amount of friendships come and gone through the years, I meet someone, we fall apart, I move on, pretty average 'life stuff' I guess.

BUT, there's been one reoccurring problem: Every friend I've had who was single when we started being friends and dated while we were still friends eventually became a different, douchier version of themselves, like fucking clockwork it is driving me insane.

Like my third ever friend, when we met he had JUST broken up with his girlfriend or some shit, like a year and a half later he dates someone ELSE and immediately becomes unbearable.

My very first friend, best friend of seven years, all of it reduced to nothing over a guy who keeps manipulating her.

At first, they broke up, she couldn't handle it for A WEEK, they got back together after a single fucking week, after going on and off for FOUR YEARS.

I stfg this guy always threatens to kill himself whenever she tries to leave him, but they started dating again after he dumped $150 dollars on her and now she refuses to actually communicate anything to me, talks about wanting to actually marry this asswipe.

Am I insane?? Is there something wrong with me?? Am I subservient to the inept consequences of dating?? Why does nobody else talk about this it's happened to every single person I've known.