Why does he trust me with his secret?

We're close friends and one day he just talked to me about how his p***s is a source of insecurity and how his is one of those really small ones. I was understanding and supportive and he was so surprised that I was. He kept saying how me, a woman is not teasing him and making jokes, because girls have been hurtful towards him in the past. I don't understand why he felt he needed to share that with me. He's really nice and we have fun conversations otherwise.
Why does he trust me with his secret?
Post Opinion