Complex sentence: Keane, who habitually referred to himself in the third person, took special pride in the eyes, which were part of the reason for his commercial success, but failed to attend a "paint off" in 1970, where Margeret produced a painting.
Split into simpler sentences: Keane, who habitually referred to himself in the third person, took special pride in the eyes, which were part of the reason for his commercial success. Walter failed to attend a "paint off" in 1970, where Margeret produced a painting.