It didn't take him long to figure that they were all gassed as his gap got over 1:30 and there wasn't anything Astana or Movistar could do. Having the discipline to hold that advantage shows strength of legs and mindset. He appeared smart enough to secure the win as much as the gap, too.
Movistar on that stage didn't have their radios working. The rain killed their radios and the riders on that team had no idea how far away Pogacar had gotten. Valverde said on the final climb fans were yelling at him that he was in danger of loosing his 2nd place on the final podium and when they realized he didn't know he was getting time gaps yelled to him by fans on the final climb. That's why he went when he did. I don't think the teams expected Pogacar to do what he did. The only two riders who may have been able to do something were Roglic and Valverde who kept their spots by doing what they had to do.