Is that it provides a lot of socially isolated people (in more ways than one) a safe arena to allow themselves to feel complex and honestly embarrassing emotions towards a charming person. You can get way into the weeds about like parasociality or whatever but 90% of the time it's just really funny.

Idol 10-15 years younger than me posting on Instagram: Are you guys gonna have a good day today? You better promise me!! Lets all do our best!
Me, fighting back tears: Yes Ma'am!!!!