Complex sentence: Foraker was astonished when he learned that Hanna was seeking the Senate seat, not knowing that the industrialist had political ambitions, and feeling that Hanna's campaign activities did not qualify him for legislative service.
Split into simpler sentences: Foraker was astonished when he learned that Hanna was seeking the Senate seat, not knowing that the industrialist had political ambitions. He felt that Hanna's campaign activities did not qualify him for legislative service.