Also schoolboy French speaker, but my assumption is that it's a malapropism: "Les Canadiens sont inquiets du coût de la vie!" would mean "Canadians are worried about the cost of living", and my guess is "cul de la vie" is how some heard his accent.

Apparently his French is pretty terrible too.

> Carney tripped up, most notably when he said, “we agree with Hamas,” instead of “we agree about Hamas,” to the delight of Conservatives all over social media.