Complex sentence: Montalvo, a dedicated champion of democracy, was said to have a lucid and inquisitive intellect and a strong, semi-romantic temperament, Montalvo turned his vivid style to a variety of cultural, philosophical, and historical themes.
Split into simpler sentences: Montalvo, a dedicated champion of democracy, was said to have a lucid and inquisitive intellect and a strong, semi-romantic temperament. He turned his vivid style to a variety of cultural, philosophical, and historical themes.