Roglic has a history of crashing. One of the top rules in cycling is don't put yourself in a bad position. Much like driving a car leave yourself an out if something goes wrong in front or next to you. As your team's GC, stay next to the team rider assigned to guide you in the flats and then maybe another one in the mountain.
Also riders riding on their own edge are more likely to crash. Everyone can get tired and bike handling suffers.
There goes Primoz' hopes for a podium placing. He looked pretty banged up as he crossed the line.
the dude cant get a break. A very freak crash , only he of all the GC contenders gets the worst of it. Why did his team not keep him in the front.