Who is credited with ultimately being responsible for establishing classical painting as an important component of 17th-century French art?

Nicolas Poussin

Explanation:

Nicolas Poussin was a French Painter from the seventeenth century who spent most of his life in Rome painting for private collectors. His style is defined by art historians as "classical baroque".

His paintings were classical because they sought clarity, rationality, and emotional restraint, but more importantly, because they often referred to themes of Ancient Greece and Rome. It was also Baroque because of the refinement and technical dexterity that he required to complete his works.

His was an inspiration to both Jacques-Louis David and Jean-Auguste-Dominique, who would define the Neoclassical style in France a century after.