Archangels - Bema Vault of Hagia Sophia

There are two archangels in the bema of Hagia Sophia, of one only the feet nd the tips of the wings survive, the other is almost fully preserved

Nick Long Jr. and Ancestry.com

Nick,was one of the stars of "Broadway Melody of 1936" - a TCM classic.  His co-stars were Robert Stack, Buddy Epsen and Eleanor Powell. Why did his career go down the tubes?