I think you're giving Trudeau too much credit...it's not about knowing or not knowing, analysis of outcome wasn't even a part of his thought process.
When Trump was announcing that America was no longer a doormat for the rest of the world, Trudeau got so giddy and excited he just couldn't possibly control such an irresistible opportunity to signal his virtue and declare to the world that the Canadian border was open to all. Like a fat kid on a twinkie, he was helpless to the urge to display his pretentiousness and moral superiority to the world ...call it a case of premature solicitation.
No...as one prominent politician put it so succinctly, Trudeau has the political depth of a fingerbowl...it is impossible to expect a person of such capacity to entertain reason or rational judgement in his thought process, or even assume he has a thought process.