Complex sentence: The NFL kept the post at the goal line until 1974, when they were moved back to the rear of the end zone in 1974, as a result of the narrowed hashmark distance of 1972, which had made for easier field-goal angles.
Split into simpler sentences: The NFL kept the post at the goal line until in, when they were moved back to the rear of the end zone. This was partly a result of the narrowed hashmark distance of, which had made for easier field-goal angles.