Supply and demand. Whether people accept it or not. After the 50s, Football became THE American sport. Colleges starting recruiting more, and thus, more and more black kids had the chance to play the most popular sport. People need to remember, that baseball desegregated first. So it really didn't have to do much with how players were being received back then. Football exploded, and more and more kids, black and white, started playing it.
Its silly to say that MLB discriminates, and it royally ticked me off when Torri Hunter said back then that Latin players didnt count. Unless you're an African American, being black Dominican, Cuban or Venezuelan didn't count.
The South, and its football factories, particularly in Florida, Texas, Lousiana, Alabama, revolve almost every step of a kids development into football. The most popular sport in school is football, followed by basketball, then baseball. Its supply and demand.
Baseball is THE sport in some Latin Countries, because it became a fabric of their culture. The South and some other states are the same way. Especially since football can be played almost year round in any weather.