I think the looks on Dumoulin and Van Aert's faces were disbelief at Roglic's collapse as much as they were to do with Pogacar.
The fundamental essence of sport is its capacity to surprise; that instance where an athlete or a team pulls out a performance which goes so much against the received wisdom or expectations that we are all left shocked and astonished. We saw that yesterday. The expectation was that Roglic would defend his lead and win the Tour, as we thought would happen before the race and was reinforced throughout by his, and Jumbo-Visma's, performance.
I don't know if Pogacar is doping or not, but his evolution as an athlete follows the usual pattern of a young prodigy; he won the Tour de l'Avenir two years ago, as Bernal did before him, put in an amazing first season as a WT pro, as Bernal did before him, then wins the Tour with a stand out performance deep into the third week of the race, as Bernal did before him. He's looked like Roglic's main challenger since the Pyrenean stages and a lead of less than a minute going into a final TT as hard and unusual as yesterday's was never enough to be certain of victory. If you look at Roglic's performances in a final TT in a GT, he's always done worse than expected so when you break it down, his performance yesterday wasn't atypical. With Pogacar, because of his youth and lack of a body of results, we don't have a yardstick with which to measure him. His final stage win in the Vuelta last year, which also secured his podium place, was a 40 km attack on the penultimate stage of the race, so clearly he has the recovery characteristics a Tour winner needs.
Time will tell if he's doping or not, but I don't think you can tell from a one off performance like yesterday's, no matter how surprising it might have seemed.