Complex sentence: He had been exposed to Veblen's thought all along the way, most systematically at Columbia, where he worked closely with John Maurice Clark, and took Veblen's work as the point of departure for his professional work.
Split into simpler sentences: He had been exposed to Veblen's thought all along the way, most systematically at Columbia, where he worked closely with John Maurice Clark. Brady took Veblen's work as the point of departure for his own professional work.