Just some wild guesses: First explosion related to second stage (upper). Second explosion related to first stage's fuel igniting (I was expecting some much big

Just some wild guesses: First explosion related to second stage (upper). Second explosion related to first stage's fuel igniting (I was expecting some much bigger, but likely there was already little oxygen left in that area and why it burned for so long. Third Explosion was the satellite's internal fuel (Hydrazine or something like it) detonating due to the fall damage and contact with the rest of the flame.