Disclaimer: I am not trolling, I am an autistic person who doesn’t understand so many social nuances. Also I am from New Hampshire (97% white), so I just don’t have any close African-American friends that I am willing to risk asking such a loaded question.
How did this become a stereotype? Doesn’t everyone love fried chicken and watermelon regardless of skin color? They are both delicious.
It became associated with black people as the food was relatively cheap and therefore commonly eaten by black people. Then it became integrated to comedic shows of people doing blackface as a way to deride black people.
Everyone loves fried chicken and watermelon. The problem isn’t the food, but cultural stigma attached to it in certain cases.
It became associated with black culture because black people tended to have larger backyard gatherings, which means feeding a lot of people. They are also historically marginalized, and had lower incomes as a result. So not only were they feeding more people when they had parties; They were doing it for cheaper. Watermelon is a cheap and easy way to feed a dozen people, and fried chicken is cheaper than other forms of protein like steaks. Yes, both are delicious, but the stereotype happened because it was both cheap and could be served in large quantities for larger backyard parties.
So basically it became a stereotype because black people knew how to have a good time and throw a party with lots of guests and delicious food?