What Brexit did impact it was that it removed EU cabotage and availability of drivers. For example, cargo would arrive on a RoRo ship in Dover, without changing to a british driver. The same driver could take other cargo while in UK (for example having delivered to point A, then taking a load from point A to another british location at point B, and finally taking a load from point B to a continental destination at point C). With Brexit, you suddenly have extra demand (as even with dimnished cargo traffic you need more drivers to service ports as cargo no longer comes with its own drivers) and inability to hire (whether complete firms through cabotage laws or simply due to smaller pool of candidates.)
That's not to say that the UK government isn't characteristically unprepared, despite months or even years of warnings about these very issues, or that they couldn't have done better to mitigate problems.
What. A. Coincidence.
(could well be true - but i did laugh out loud)