Complex sentence: He painted mostly religious chiaroscuro scenes lit by candlelight, and after centuries of posthumous obscurity, during the 20th century, he became one of the most highly regarded of French 17th-century Baroque artists.
Split into simpler sentences: He painted mostly religious chiaroscuro scenes lit by candlelight. After centuries of posthumous obscurity, during the 20th century he became one of the most highly regarded of French 17th-century Baroque artists.