He fell because he lost feeling in his hands and fingers and couldn't get grip on the bars, you can imagine how cold it is there under those conditions.....Hope he will be ok
Because they are constantly pushing their bodies and the friction of their tires on the road to the absolute limit. Add in cold weather and wet roads and you get lots of crashes. In this case his hands were so cold and numb that when he tried to put more power out to sprint for the line his hands slipped off the bars. Even on dry, warm days they are racing their bikes at 30mph within inches of each other so even slightly unexpected changes in speed or direction can cause them to bump into other riders.
They are going much faster and aggressively. Also they are riding for 100+ miles a day. And occasionally a bit of bad luck that gets magnified in the spotlight.
