For those who didn't click on the link, here's the video. Camera from bike 2 ahead of the crash, facing backward through turn 5. The slow motion is annoying, it would be easier to interpret if there was a full-speed version as well.
Link to original page on YouTube.
Sandbag or not, it still looks like he would have crashed pretty hard. Bike already out of shape before sandbag, and plenty of ruts in the runoff already.