What went wrong is that 1) Tesla never made a low-end vehicle, despite announcements, and 2) all the other US manufacturers treated electric as a premium product, resulting in the overpowered electric Hummer 2 and F-150 pickups with high price tags. The only US electric vehicle with comparable prices in electric and gasoline versions is the Ford Transit.
BYD says that their strategy for now is to dominate in every country that does not have its own auto industry. Worry about the left-behind countries later.
BYD did it by 1) getting lithium-iron batteries to be cheaper, safer, and faster-charging, although heavier than lithium-ion, 2) integrating rear wheels, differential, axle, and motor into an "e-axle" unit that's the entire mechanical part of the power train, and 3) building really big auto plants in China.
Next step is to get solid state batteries into volume production, and build a new factory bigger than San Francisco.