It's crazy: Donald Tusk told the UK way back in March to 'concentrate on getting the Brexit deal through by 31 October [six months]'. What do we do? Leave it to the last week.
Of course we do.
It's obvious that any Brexit deal would fail to pass on its own merits given that half the country wants to Remain and that of the other half there are many who want to retain EEA membership and others for whom anything other than a complete separation from the EU is anathema.
Theresa May's deal (and Boris Johnson's deal which is the same deal in floppy hat an glasses) attempted to square that circle by retaining as little link as possible with the EU without severing ties altogether. It was still too close a relationship for the EEA whilst being too distant for others.
The only way to pass a deal is to create such a time pressure that MPs are unable to review the deal properly and/or feel obliged to accept any kind of a deal to avoid something far worse (either no-deal or no Brexit depending on your point of view).
It's never been about the UK's best interests, it's been about political theatre and avoiding blame for the inevitable bad outcome