Complex sentence: As late as 1924, Frederick H. Gillett was Dean, and also Speaker, before becoming a Senator; modern Deans move into their positions so late in their careers that a move to the Senate is highly unlikely.
Split into simpler sentences: As late as 1924, Frederick H. Gillett was Dean, and also Speaker, before becoming a Senator. Modern Deans move into their positions so late in their careers that a move to the Senate is highly unlikely.