The thing is that there were people on the left who kind of saw this coming, even if they only saw it partially. And not only intellectuals like Christopher Lasch or Maurice Glasman.
The period after the Brexit referendum was very revealing. I'm not looking to argue here about whether Brexit was a good or bad thing, I'm just making a point about the popular will. Almost all MPs said before the vote that they'd respect the outcome, and then when the outcome wasn't what they expected, the majority of them spent the next three and a half years acting like a toddler refusing to put his wellies on.
There was a small group of Labour MPs in heavily Leave-voting Red Wall constituencies (Stephen Kinnock, Caroline Flint, Gloria De Piero and a couple of others) who said "we voted Remain, we don't like the outcome, but we promised to respect the result and we'll have to do that, and get the least damaging exit deal". Nobody listened to them.
There was a similar thing in Plaid where Adam Price had a rush of blood to the head and thought Plaid could become massively popular by jumping on the second referendum bandwagon, to which Leanne Wood responded (I'm paraphrasing here) "you must be fucking joking, there is no way on earth I can sell that to Rhondda voters".
I'm not making an argument about the merits of Brexit here, just saying there was a point of view that our leaders might have benefited from paying attention to. I think all those people are now out of active politics except for Stephen Kinnock, who was forgiven due to being regime aristocracy.
The point about the consent of the governed is that there has to be a mechanism where the governing class can listen to the people and receive feedback. You can't have a Parliament full of Rory Stewart types telling us what we should be thinking. That way lies disaster.