All the things said in this thread, but I will add one more: exposure and encouragement.
Working in business I came to realize there are so many types of businesses we are not exposed to and I grew up middle class and got a good education. Light manufacturing, distribution, and some others don't really make it onto Black folks radar to start a business both because of capital hurdles and exposure. When most Black folks who can get capital want to start a business, they already usually have exposure, and a social network, for sports, entertainment, and to a lesser extent real estate and some fields in finance. There is an established Black presence and network you can capitalize on.
You notice how other ethnic groups focus in on certain businesses. It isn't because they all have some brilliant idea, they funnel into what they are exposed to and then the next generation goes into something bigger---or not.