I don’t necessarily think the size of a guy’s cock makes them a cuckold, however in my personal experience, it definitely contributes to my feeling of inferiority and aids in my acceptance and gratification of being one. Personally speaking, I could tell my wife was disappointed at the size of my cock. From the first time we slept together, so the lifestyle once she accepted, it really fit us like a glove, but after being in the lifestyle, I have befriended a couple of guys with a pretty big cock. It just might not work well enough for lover. They may not perfectly fit their partners ideal for what a true alpha male is. So it may not be the only factor but I definitely think it is a major factor.