Those are small parts, though. The interesting part is the E-axle. BYD builds a unit with an integrated motor, differential, axle, and wheel hubs. That, plus an electronics box and battery, is the power train. This simplifies vehicles considerably.
There are E-axle teardown videos. There's no big secret about how to do this. Copying this is hard for Detroit, because they have a huge investment in "engine plants". With this design, BYD doesn't need standalone engine plants.
Tesla ought to be doing this, but they're into performance, not cost. They want to put two or four motors in a car. BYD does make supercars, to show off, but their volume products are reasonably good cars with E-axles and lithium iron phosphate batteries, which work fine. (It's not clear that Tesla is even into car design at all any more, but that's another issue.)
Detroit ought to be doing this, but they insist on making electric cars that are modified gasoline cars. Ford has an electric Mustang, an electric F-150, and an electric Transit. Chrysler doesn't even make cars any more, just one minivan. GM has a good Bolt now, which they are killing to appease Trump.