Conversation so far:
When did Oscar Robertson play for the Bucks?
Prior to the 1970–71 season, the Royals stunned the basketball world by trading Oscar Robertson to the Bucks for Flynn Robinson and Charlie Paulk.
what position did Oscar Robertson play for the Bucks?
Oscar Robertson played Point guard for the Bucks
who was Oscar Robertson's coach before the Bucks?
Oscar Robertson's coach before the Bucks was Bob Cousy
what team was Oscar Robertson with before the Bucks?
Before playing for the Bucks, Oscar Robertson played for the Royals

Question: why did he leave the Royals for the Bucks?
Self-contained rewrite: why did Oscar Robertson leave the Royals for the Bucks?