Mozart was one of the top Classical period (1750-1830) composers, and is certainly the most famous. He was a genius, he was prolific, he was famous during his day, and among classical composers he is often considered the best. To this day he is a household name, and his operas, symphonies, and chamber music are commonly performed.

Bach died (1750) before Mozart was born (1756). He composed in Baroque (1600-1750) counterpoint. He produced an inhuman amount of music, as in he had to be writing constantly. While he lived he was not famous, but he was known in smaller musical circles. After his death, his music was mostly forgotten, and baroque counterpoint in general was outdated and not often used in the classical style. It wasn't until the 19th century that he was rediscovered, having his works re-published and performed. His music is subtle and complex, maybe I can describe it as a crystalline mathematical profoundness.

Among many Bach is considered the GOAT. I could believe that a super-intelligent former human AI musician would find his music interesting. Whereas Mozart was merely the greatest Classical composer. But of course, Sterling is also lobbing a grenade into an infinite flame war about which music is better. So that's a fun way to rile up the Mozart stans.