I'm not British and I don't follow it's daily politics particularly closely, so I might be wrong, but to me it seems like Brexit made the cynicism in politics abundantly clear.
I'm thinking about Farage feigning amnesia about the bus ads right after the vote, Johnson campaigning for Brexit with "conviction", then passing on leadership in favour of a remainer when it came to implementing it. And on the other side there's Labour, their complete lack of a position on the matter and a strategy that seems to be most concerned with what's best for Corbyn. To the point where people who made up basically half of the vote had to create a new movement, which if that earlier tweet is to be believed is also being lead by someone whose primary motive isn't Brexit.
This is might be the most important political issue in people's lifetimes and yet it couldn't be clearer that their representatives are most concerned with how to use it for personal gain, be it money or power.
I have absolutely no faith in Labour to actually do something meaningful about Brexit, so I can understand people who say that if no one is fighting for them they might as well accept the deal that's on the table.