Complex sentence: Winfield's immediate authenticity led to his 20-year run as the Marlboro Man, which lasted until the late 1980s, upon Winfield's retirement, after which Philip Morris reportedly spent $300 million searching for a new Marlboro Man.
Split into simpler sentences: Winfield's immediate authenticity led to his 20 year run as being the Marlboro Man, which lasted until the late 1980s, upon Winfield's retirement. After Winfield's retirement, Philip Morris reportedly spent $300 million searching for a new Marlboro Man.