What was Leonardo Da Vinci interested in accomplishing by creating his work?

Leonardo was interested in many tjings; engineering, painting. He designed machines, made studies about human body for his works. His paintings are made with the technique of sfumatto, with slightly blurred contours. His subjects are both religious, as in the Last supper, and pagan, as in Gioconda. This famous woman seem to have been the wife of a merchant named Giocondo, so why it's so named, though some think it was a self portrait or of a lover of the King of France, country whete Da Vinci ended his days. The picture was stolen from The Louvre in 1909 and returned two years later