I believe that the marshal with the green flag at the back of the grid at the end of the parade lap (signalling to the starter that the last car has stopped in its grid place) originates from that lap 1 accident at Monza in 1978.
That time the starter sent them off too early - and so some cars had stopped and were in 1st gear waiting, but some were stopped and still in neutral so were caught out, and others were still rolling forward and in 1st gear coming down from 2nd gear etc so got a flying start - all of which was a contributory factor in the pile up accident near the 1st chicane.
(The possibility of a coked up or stoned Hunt can't be discounted as a factor either I reckon - he falsely claimed that Patrese had hit him and triggered everything - the start of a feud which only concluded with Hunt's death in 1993)
There was a (silly) argument put forward at the time that no driver should have weaved right or left but just all driven away in 2 straight lines behind one another - and if all doing that there would've been no accident - but has any GP ever started like that?
(Patrese came towards Hunt on the narrowing Monza track as the cars neared the 1st chicane and Hunt moved away in avoidance - but that simply resulted in Hunt hitting Peterson who was already being squeezed by Hunt. Peterson's car then hit a barrier and caught fire and then was hit again at least once by Brambilla - who was driving a Surtees I think and was himself badly injured)
I was only a little boy at the time, and my most vivid memory of it was (on Grandstand or Sportsnight etc days later) of the helicopter camera looking down at the fire whilst Murray Walker named the drivers who were rescuing Peterson (Hunt, Daly and Regazzoni were 3 he named).
I think Sid Watkins in the medical car and the medical helicopter were other consequences - I think on the day they had to appeal over the loudspeaker for any doctors who were in the crowd!