Complex sentence: Sweden's first win was in 1974, when the quartet ABBA won the contest with "Waterloo", thanks to their Eurovision victory in Brighton ABBA went on to gain worldwide success, still being one of the best-selling pop groups of all time.
Split into simpler sentences: Sweden's first win was in 1974, when the quartet ABBA won the contest with "Waterloo". Thanks to their Eurovision victory in Brighton ABBA went on to gain worldwide success, still being one of the best-selling pop groups of all time.