Complex sentence: Wilson was a friend of Boston founder John Winthrop who was a layman in the church, and it was Winthrop who took advantage of a rule requiring unanimity in a church vote, and was thus able to thwart the appointment of Wheelwright.
Split into simpler sentences: Wilson was a friend of Boston founder John Winthrop, who was a layman in the church. Winthrop took advantage of a rule requiring unanimity in a church vote, and was thus able to thwart the appointment of Wheelwright.