Complex sentence: Cooper came out of Philadelphia and was trained in his early years by ex-champ Joe Frazier, and rose in the rankings with a series of explosive knockouts in the Cruiserweight division.
Split into simpler sentences: Cooper came out of Philadelphia and was trained in his early years by ex-champ Joe Frazier. He gained attention and rose in the rankings with a series of explosive knockouts in the Cruiserweight division.