I don't think any show since Breaking Bad has pulled off the "These people we have gotten you to root for are actually terrible" gambit as well as S4 of The Crown does. Peter Morgan has used Diana as a kind of scouring device that exposes everyone else as failed humans. >
Olivia Colman is such an empathetic actress that it's shocking that she doesn't flinch from the indictment that the show asks her to embody--the idea that these people are devoid of a vast range of human feelings, vaguely maddened by knowing that, and incapable of fixing it.
It's also an extraordinarily elegant piece of storytelling in that seasons 1 and 2 felt like they were from the inside out; we comprehended this world through the eyes of a limited but essentially sympathetic young woman asked to assume an absurd set of duties at a fraught time.>
But season 4 is very much from the outside in: We're now asked to look at this family largely through the eyes of outsiders--Diana, Thatcher, the intruder in episode 5--and their appalled incredulity at what they see becomes our own. Anyway: It's really good, you should watch.