Complex sentence: During the 1960s, this led to a huge underestimate by the artist on the value of his works-as a result, he agreed to consignments of dozens of paintings to the gallery and collectors without appreciating the full value.
Split into simpler sentences: During the 1960s this led to a huge underestimate by the artist on the value of his works. As a result, he agreed to consignments of dozens of paintings to the gallery and collectors without appreciating the full value.