How much attention were you paying?
In the private hospital scenes, he realises its WORSE than the NHS, he realises these people are being fleeced for huge amounts to line fatcats pockets, like those of his bullying arsehole consultant... but the care provided is worse, the services fewer and when the woman he is treating is at risk.. she has to be ambulanced to a real, NHS hospital to save her life.
The grass is very much NOT greener and it clearly sickens him.
his junior colleague killing herself - he realises she's been bullied and he has been part of that, because he was bullied and thats how the system worked, everybody shits on the one below them. He tries to break that but its really way too late and she's been under pressure from many more people than just him.
Im not saying hes a nice guy, im certainly not saying he is hysterically funny or that any of this dark humour is particularly clever or new or groundbreaking - it isn't.
But if he'd simply written a book about how dire the NHS is, how awful it was doing his job and how bad at it he was... no one would read it, no one would have made it into a TV series and we would not be talking about it for the umpteenth time.