As a child that is one of the first relationships you form and if that trust is broken it is hard to regain trust with anyone else so someone with this disorder might tend to shy away from social activities and get anxious about any sort of human interaction. Therefore, Lars is terrified of trying to gain trust with someone because of fear of abandonment which is why it is so hard for him to trust Margot but easy for him to trust Bianca because he controls whether she leaves him or