Complex sentence: The modern rock radio format experienced a substantial growth in popularity during the decade, with the success of Nirvana's 1991 single "Smells Like Teen Spirit" marking a "return of the crossover rock hit".
Split into simpler sentences: The modern rock radio format experienced a substantial growth in popularity during the decade. The success of Nirvana's 1991 single "Smells Like Teen Spirit" marked a "return of the crossover rock hit".