Final answer:
The CIO broke away from the AFL due to its focus on organizing industrial workers in mass production industries, using aggressive tactics to secure better wages and benefits for employees, which was successful with companies like GM and US Steel.
Step-by-step explanation:
The CIO split from the AFL because of the CIO's emphasis on organizing industrial workers in mass production industries. The CIO, or Congress of Industrial Organizations, was formed as a response to the forces of industrialization which shifted the nature of labor.
Under the leadership of individuals like John L. Lewis, the CIO was proactive and sometimes aggressive in its tactics, as seen in instances like the United Auto Workers' sit-down strike. The CIO successfully compelled companies like General Motors and US Steel to negotiate, resulting in increased wages and improved benefits for employees.
The rise of organized labor encountered many challenges, especially as the economy evolved and businesses sought ways to undermine union influence, such as relocating operations to less union-friendly regions or abroad.