Complex sentence: Prior to the 1970s, many states crowned state champions through polls, but playoff systems have become nearly universal since then and most states have steadily increased the number of teams eligible to participate and total number of classifications.
Split into simpler sentences: Prior to the 1970s, many states crowned state champions through polls, but playoff systems have become nearly universal. Since then and most states have steadily increased the number of teams eligible to participate and total number of classifications.