This government simply doesn't care about the economic impacts, or at the very least is too stupid to fully understand the numbers and their long-term implications for Glorious Brexitannia.
Either way, any economic strife the country experiences over the coming months will simply be used as a battering ram to force through whatever grisly trade deal they cook up with Trump and has band of like-minded nationalist twerps. "All the more reason to vote for this deal, as a matter of the utmost urgency..........", that sort of nonsense. If Labour tries to block it, the government might even be able pin the blame on them yet again.