Complex sentence: In his autobiography "Let's Get It On" famed referee Mills Lane, who had officiated at some of Bowe's fights, professed that Bowe could have been one of boxing's greatest fighters but foolishly squandered the opportunity through immaturity and lack of discipline.
Split into simpler sentences: In his autobiography "Let's Get It On" famed referee Mills Lane, who had officiated at some of Bowe's fights, castigated Bowe for his lack of maturity and discipline. Lane professed that Bowe could have been one of boxing's greatest fighters but foolishly squandered the opportunity through immaturity and lack of discipline.