Bicycling

The ASO made the decision at 1 AM to shorten the course by 6 km.

While I agree that some "fan" behavior is definitely out of line, the problem here was compounded by the fact that the shortened course meant that people who were camped out on Ventoux in the days leading up to the stage were caught in a mad scramble to move the finish line, barricades, and literally thousands of people down the mountain in short order. Since the people in camping caravans couldn't move after the road closure, they hiked down to the nearest point they could reach - meaning the non-barricaded portion of the course which was only about 600 meters or so from the finish (while a longer stretch is usually barricaded).

While the course had to be shortened because of high wind at the top, it seems they did not consider the knock-on effects of that shortening, as opposed to some other alternative in the absence of a plan to deal with 6 km of spectators squeezing into 1 km of space.

It's not entirely clear that this was spectator caused. There were several Velo News cycles which stopped ahead of that camera cycle, and if anyone has a link to a direct account of why that line of cycles stopped, I'd be interested to read it.

I'll be posting some of my photos and videos after I unpack, but to give you an idea of how quickly the crowd gathers, this was the view of the street from my hotel in Samoens at the base of the final climb to Morzine, about three hours before the race was to arrive (and about an hour and a half before the really crazy part of the day - the publicity caravan):



This was the crowd when the publicity caravan had just ended (if you ever wondered why the spectators were wearing so many matching shirts and hats):



...and this was the crowd when the GC group (and a few small but very loud thundershowers) came through:



But on the subject of:

"The TV camera-outfitted motorcycle running just a few feet in front of the riders was forced to come to a screeching halt due to the crowd blocking the road"

Here's a shot from a different perspective:



Notice that there is a lane through the crowd, but there is another motorcycle with its brake light on, ahead of the camera motorcycle, just before Porte hits the back end.

There was a line of stopped motorcycles:



...and the lane is clear ahead of the lead motorcycle.

Compounding the problem, after Froome went down another motorcycle rode over the back of his frame, breaking it, which is why Porte and Mollema could continue and Froome could not.

I'm not fond of the crazy people who cause disruptions, run alongside the riders and light of flares, but it's difficult to say this was entirely "fan behavior" that caused the crash.