I've just re-watched the entire first 2.5hr of the race, and in the process I re-watched the incident that took out the #30 (for the 4th or 5th time). This time I did a shift-U and placed the camera looking toward the bridge overpass, just behind the cars that got in trouble. I watched the replay at .25x speed and looked to see when the brake lights came on for each car involved.
What I saw was this:
The #29 car, far ahead of the cars involved, was lagging back a bit from the car in front of him. This, in concert with the slower corner ahead, caused the cars behind him to bunch up. The last of the cars in this bunch was the #26. Behind the #26, the #16 had a bit of a gap and was on the gas trying to close it up in preparation for the green flag. The #26 was going very slowly by the time the accordion effect took full effect. The #16 got on the brakes pretty early, but was unable to slow enough and hit the rear of the #26, sending them both spinning, and blocking most of the track.
The #30 got on the brakes as well, but a little too late, and hit the #16. There was a brief spike of lag involved in the contact, which erased the #30's forward momentum and brought it to a dead stop, broadside to the track. At this point, the #13 and #03 cars came into the picture, already on their brakes, and again were unable to slow before making contact. The #13 hit the #30 broadside and once again lag seems to have been involved, as the #30 just took off and flew down the track and onto its side behind the barrier.
The actual cause of the incident was the #29's slowing at the middle of the field, and the resulting accordion slowdown behind him. The secondary cause is the timing of the #16's attempt to catch up to the #26, and the reaction time involved in slowing when he saw the #26 and cars ahead of it had slowed.
I hope you can see where it's difficult to see who to blame, and even more difficult to penalize.
Rest assured that we are working on new SC procedures to try to avoid these incidents.