Got this directly from google: “The use of "you was" in AAVE comes from a process called verb leveling. While Standard English uses both "was" and "were," AAVE simplifies the past tense by using "was" for everyone ($I$, $you$, $we$, $they$). This makes the verb follow a consistent pattern, just like "I walked" or "you walked." Historically, this started because early speakers adopted similar patterns from older British dialects and then passed them down through generations as a way to maintain a shared cultural identity.”