I think being a minority and sort of always sticking out, makes them more assertive. They have to be.
Black skin also has better muscle definition, so if they work out, they see results faster, and muscles looks really nice on black skin.
Not all Black men are like that of course, there are a lot of fat, ugly, scrawny, short, loser ones out there as well. It takes more than for him to be Black to be attractive.
Personally, I love athletic, dark skinned Black men with really African features, like thick lips and wider noses. It's the difference, the muscle definition, and the soft features that turn me on. I also like the assertiveness that jocks have.
The thing about big d***s isn't really true, although I do notice they have bigger balls on average.