Wtf, why didn't they contest that, could have been bronze. Rules are pretty clearcut:
17.2.2 if another athlete is found by the Referee to be responsible for the jostling or obstruction, such athlete (or their team) shall be liable to disqualification from that event. The Referee may, if they are of the opinion that an athlete (or their team) was seriously affected, in accordance with Rule 18.7 of the Competition Rules or Rule 8.4 of the Technical Rules, order that the race (for one, some or all of the athletes) be re-held excluding any disqualified athlete (or team) or allow any affected athlete (or team) (other than any disqualified athlete or team) to compete in a subsequent round of the event.
Only disputable part is maybe whether its really an "obstruction" I think