Look at the overhead shots. Coquard moves into Gerrans, he has nowhere to go, Cav is going for a gap and moves a bit left, desparate to get the win on stage 1 which OPQS would want. Doing his job. gerrans in a sandwich, handlebars clash with Coquard's. Gerrans in impossible situation as is Cav.
If anyone is a cause, Coquard has a share of that, but as I see it, a racing incident between highly committed sprinters which went wrong big style. Another time they would have fallen, rolled, grazed, and fought another day. The injury was really bad luck, but that's always a risk when you are a potential stage winner and a target for all the other fast men. It's really good to be a domestique, have done your job, and be able to sit back and not be involved!
The other interesting thing is Froome in 6th., what was he doing there, kept near the front by the team and taking a little chance to show himself early?