Mexico asked nicely and said they'd work with us, and pointed out an existing trade agreement (that also covers Canadian goods) - that's what Trump wanted, someone who will negotiate for the betterment of both countries.
Canada shit its pants and can't even call their nanny to clean it up because they prorogued their parliament. I'd like to think the extension is to give them time to meet, discuss, and decide on what to do (which should be to meet Trump's demands) because if they do what Trump wants, the tariffs go away anyway.
Watching how both countries react to the same demands has been interesting, and I think Trump has given both countries plenty of notice, plenty of extensions, plenty of chances to do what he asks. If April 2nd rolls around and Canada is still playing prissy pussy, those tariffs are gonna HURT. Gonna be really funny when Mexico does what it should, prospers, and Canada withers into less than a US territory.