Complex sentence: The new team entered the North American Soccer League, which was in its fourth season, and bankrolled by parent company Warner Communications, became the league's most successful side, winning a record five championships in front of the the league's largest crowds.
Split into simpler sentences: The new team entered the North American Soccer League, which was in its fourth season. Bankrolled by parent company Warner Communications, became the league's most successful side, winning a record five championships in front of the the league's largest crowds.