Complex sentence: He also took no role in the subsequent impeachment proceedings against Johnson (which, in part, centered on Johnson's removal of Stanton); whereas, none of the principals in the impeachment matter benefited from it.
Split into simpler sentences: He also took no role in the subsequent impeachment proceedings against Johnson which, in part, centered on Johnson's removal of Stanton. In contrast, none of the principals in the impeachment matter benefited from it.