I’m not surprised some think MvDP should have won the award, or even Pogacar. But I’m shocked people think Vingegaard does not deserve it. IMO (cuing a subjective take here), it should have come down to Vingegaard and MVDP.
Vingegaard, as 
@proffate said above, dominated the biggest race of the year with the biggest ITT performance in at least a decade. He also was second in the Vuelta and was a huge part of everything that played out, somewhat acting as disruptor, media manipulator (outplaying Roglic for sure), and king maker. And he won Paris-Nice and The Dauphine. Did he win or even ride a classic? No. But he won on the biggest stage and had the biggest Oh ***! moment of the year.
MVDP had a comparable season on the classics side, with his Worlds domination equivalent to Vinge’s Tour. Two other monuments but a helper in the Tour. Since the Tour > classics, I think they went for Vinge. He clearly would have deserved the award, too.
I don’t see how Pogi gets it. He was crushed in the Tour, he was crushed in Worlds, he didn’t ride the next tier of biggest races (Giro, Vuelta, I’d even sneak in Paris-Roubaix). He performed near the top in a crazy diversity of races and IMO is the best all-around rider, and my favorite rider among the 3, but his top results just aren’t as good as the other two’s, IMO.
As much as I love Roglic, he needed at least Vuelta or Lombardia, maybe both, to win this.