How did this get such great reviews?

Maybe it's the concept, the plot, the acting and the visual effects is what gave it great reviews.

This is not an uncommon phenomenon. A film such as this may bomb at the box office for various reasons; It may not be to everyone's taste, receive bad publicity or perhaps the distributors dropped the ball. However, such films may find a cult following and dedicated fan-base, hence the positive reviews.
The opposite is also true. Quite often, popular films an even those generally regarded as classics sometimes receive negative reviews and low ratings.

Certainly wasn't universal acclaim, but your right about it commercially going belly-up despite it being the highest grossing Canadian film of the year of its release.🐭

Critics analyse films in a much more detailed and intellectual way than audiences. It's what they are paid to do.

I loved this film but I imagine most people would find it dark, disturbing, gross or just ridiculous.