It's a form of Stockholm syndrome and a coping mechanism against immense, inescapable pain. It's the 4th F of trauma coping mechanisms: Fight, Flight, Freeze, Fawn.

When something is very painful and inescapable you can: Fight it, run away from it (not talk about it, ignore it, pretend it's not there or won't happen), freeze (dissociate, ie shut down emotions, be stoic, feel nothing or little) or fawn (appease, please, embrace the pain in order to feel a sense of control over it, and some release from the torment of powerlessness+pain).