Complex sentence: Not only did Toste become interested in investigating the history of Puerto Rico, but, he also took an active interest in the island's politics and was the founder and director of a publication called "El Ramillete".
Split into simpler sentences: Not only did Toste become interested in investigating the history of Puerto Rico, but, he also took an active interest in the island's politics. Toste was the founder and director of a publication called "El Ramillete".