Complex sentence: The newly completed arena proves lucky at the Rangers draw record crowds and finish their season in 1st place, and continue to not only win the league championship but the National championship as well which was then known as the Centennial Cup (RBC Cup today).
Split into simpler sentences: The newly completed arena proves lucky as the Rangers draw record crowds and finish their season in 1st place. They continue to not only win the league championship but the National championship as well which was then known as the Centennial Cup (RBC Cup today).