I think this accident today may have revealed how Rosberg has been getting the upper hand at the starts this year. He may have figured out that the energy recovery mode gave a better traction from standstill than the normal startoff mode. While Hamilton has been following the instructed start procedures, Nico may have been using the unorthodox energy recovery mode. Every other race before today, Hamilton has had crashes at the first corner, hence has not been in the position in this grand prix to challenge Rosberg into the second corner.