Follow up, what events in music spurred on the inclusion of conductors? Were conductors added at a certain point in history due to some development in music (such as the use of large orchestras)?
You're quite off on this one. Conductors were in wide use even in the 17th century. Even Lully, the example you cite died in 1687. Bach conducted from the organ in the 17th and 18th centuries, and it wasn't uncommon in the 18th century to have the composer conduct. And the concertmaster wasn't the only musician conductor, as it would make more sense for the harpsichord, organ, or continuo to direct in a lot of instances.
As for the death of Lully, the incident was witnessed, as it was during a public performance, and is referenced extensively in New Grove, so it's highly unlikely to be apocryphal.