I don't think there is any certainty yet, but there has been a report of a Maserati cutting him off before he hit the barrier and flipped. What is notable about that is that the name of the Maserati driver was released, which would lead one to believe that there may have been some contact between the vehicles that caused some damage, and thus the driver stopped. I lived in Miami for over 15 years, normally if a car cuts in front of you and there is no contact, the car will just speed away.
Again, that is pure speculation on my part, but if a Maserati is in front of an accident and in a merge lane about to enter an expressway, it's unlikely for the driver to just stop and wait around for the police to arrive.