Complex sentence: The clip exists because WSBK-TV in Boston, an independent station, was the television flagship of the Boston Bruins and had a weekly program during the season showing highlights of the previous week's games.
Split into simpler sentences: The clip exists because WSBK-TV in Boston, an independent station, was the television flagship of the Boston Bruins. WSBK had a weekly program during the season showing highlights of the previous week's games.