Well that certainly seemed a bit erratic at the end. It didn't look like the bus driver was at fault, the race organisers should ensure that there's headroom for such vehicles, or not let them down there at all. Typically they aren't moving that fast, and people have plenty of time to stop them, so I can't see how the driver could be at fault. Conceivably the team had a vehicle that was too high, but I'm betting on the banner arrangement being too low.
Presumably the change of the end to 3km (with the riders at 5km!), and then changing it back to the finish line, probably didn't exactly help the rider's concentration, so may well have been part of the cause of that crash, but it's not unusual to get crashes at this point in a stage, so it's as much down to the riders, and sheer bad luck as anything else.
Taking out all of the potential winners was a god send to Kittel, who is now in Yellow, Green and White apparently! I don't imagine he'll hang on to all of those for long, but it's certainly been an eventful day for him, I don't think he'll forget it easily!
