I think @jpop made a good point - the UK has, under Theresa May, spent 3 years kicking the can down the road. Whether they were waiting for a miracle to deliver them from the burden of having to actually do something, who knows. A more pro-active government 3 years ago would have seen issues ironed out over a (relatively) calm, longer period.
The problem the UK has with the Prisoner Dilemma is that the "deal it already has" is not one they can accept. The fact that this deal may oblige the UK to stay in the customs union until the EU consents for it to leave, makes this so.
In fact, if we go back to November 2018, when the withdrawal agreement terms were first released, Mr Macron publicly referred to how France would use the trap of a perpetual customs union to force the UK into an acceptable agreement on fishing rights.
The real problem is that we have to seek a revised withdrawal agreement because we cannot accept being trapped in a customs union with no legal way to exit. I am not being funny here; the UK cannot "leave" the EU by agreeing to be tethered with no departure rights. It is a fundamental non-starter, as both our government under Theresa May and the EU fully realise.
A "no deal" outcome is a bad one, yes, and I hope we can avoid it. But is it as bad as being chained to the EU customs union until they say we can leave? Probably not.
Still, at least we can say Boris Johnson is a principled politician. By signalling he is prepared to call a snap election soon, and thus opening up the prospect of being the shortest-serving prime minister in the UK's history, he cannot be accused of introspection.
Or can he??????
I am sure the possible reactions are endless.