This is fantastic. I wonder if they could partner with the Canadian government to make this easier for their employees who need to gtfo from their home country.
The historical reason is that Canada is underpopulated for its size. As far as STEM, a large percentage move to the US, so foreign STEM workers are needed.
In addition, Canada is doing a lot of PC/SJW activism today, so there's that too.
2) The easiest US work visa is the TN-1 for a Canadian citizen to work in the US. Note that it's a non-immigrant visa, so if you want to stay long-term in the US, you would need to do further immigration paperwork.