Why wouldn't he? BYD and other cheap BEVs from China directly threaten American jobs, and not the poorly paying kinds either. I see no rational reason why an American president wouldn't do everything in his power to protect American interests.
And for the environment I don't really think BEVs in the shape of cars is the solution. Scooters and small motorcycles outnumber cars by far and is growing faster as well, while each individual vehicle pollute far less the sheer volume is a problem and the air quality problem they contribute to is massive. Those and trucks I feel are the important vehicles to focus on, for the environment. But it's far easier of course to market and sell cars to high income individuals, in areas with the infrastructure necessary to support electric cars.
Then there's the whole not recycling old Ecar components, especially batteries, problem. Transportation going electric will only be environmentally sound if the related recycling industries are brought to a profitable scale...
Some, not all, and not every piece of the battery either. Lots of plastics go into the production of batteries, and almost none is recycled despite batteries not having the general worries associated with recycled plastics.