Different methods of therapy appear to be equally effective despite having theoretical foundations which are conflicting with each other. The common aspect between different therapies seems to be "having someone to talk to", so I'm inclined to believe that really is what's behind the success.
This isn't true. Different methods work better for different problems. I've been in behavior health for 7 years now. It's having someone with a lot of education to talk to, someone with education in social and psychological problems and healthy coping mechanisms.