I think a key thing is that the person has to be willing to open up and trust others. They also have to put in the time getting to know the person. There's more to it than just charisma and social skills even those these 2 skills help. There's a lot of mindset involved and past experiences that may affect someone trying to get friends. Take my past for instance, I got bullied a lot and someone who I thought was a friend turned out to be a bully. It's not easy making friends after getting betrayed like that because it always come into your head what if this happens again. Maybe I made no sense but I hope I did