My bet is that the Canadian government wanted to close the border to US tourists, but in discussions with the US government it was made clear that that is unacc

My bet is that the Canadian government wanted to close the border to US tourists, but in discussions with the US government it was made clear that that is unacceptable. I think it's fair to assume that's because of internal US politics, ie. Trump wouldn't like it and it would make him look bad. There's no reason Canada couldn't close to US tourism, but remain open to commerce.