Well, arguably, they kind off got carried away by the thing they created; Brexiters pre-referendum were usually advocating some sort of soft Brexit (albeit often with conflicting demands which made it impossible; "single market access but we don't need to follow European rules" sort of thing), then there was May's Brexit which looked 'hard' at the time but soft compared to what actually happened, then Boris's Brexit, and then Truss wanted to make it _worse_. All of these things were worse than being in the EU, but the degree of badness intensified as the leaders of the movement were captured by the movement itself.
Well yeah, the population voted to jump off a cliff, and the leaders (Boris) cheered them on and promised them the most spectacular cliff jump ever just to shove it to the EU.
In a way this is populist democracy in action and is a lesson for future generations.
The leaders weren't just I'll prepared with Brexit, they head-on despite the consequences, since they were chasing the "EU-bad" popularity votes by pointing at the EU as the scapegoat for the UKs own self inflicted internal issues. Now the leaders have no more outside scapegoats other than COVID and Putin.