Why do we get attached to fictional characters?

I was reading some spoiler posts of a series and in its comments one user was fighting as if their life depends on it to defend that series ml, a trashy character. Even going on to say that they know that character better than the author

Recently I'll be reading some great story and go thru roller coaster of emotions and then go did I really sob over some drawings/texts

People deadass get depressed that the character they obess over is not real or they themselves can't exist in that character's universe. It even becomes a serious obsession for few where they literally feel numb irl and get emotionally disoriented

So why do we get so attached to fictional characters?