I agree on the infrastructure, but outsourcing?
Most value in any car today is added by suppliers. Thats business as usual and for a good reason. Tesla gets their cells from Panasonic, instead of building their own ones, for a reason. The same goes for the AP computer by NVIDIA. Both are very expensive parts of their vehicles, but a supplier can do it better. The same goes for many petrol cars out there and they do fine. ECU, Turbo and fuel injectors from Bosch, gearbox and steering system from ZF? Now you have a VW Golf/Jetta drivetrain and they sell like hotcakes.
Now there are parts of manufacturing a company wants to keep and a even broader part where they want to do the development, but I am not sure if the electric motor, an often used example in discussions like this, is necessarily part of it. All electric (XX torque and XX hp) motors behave the same to the consumer and the consumer has no direct interaction with them. Setting some specks like torque, hp, efficiency and NHV should be enough here. And if a supplier can do it cheaper, or better, go for the supplier. There is very little differentiation to be had. No one would care if a Mercedes electric motor would be the same one as in a Ford, the same goes for the reduction gear.
The real mistakes GM made was building a subcompact hatchback in America, not giving it AWD and not investing in a charging infrastructure. Those were dumb moves. Not "outsourcing" and "too little advertising".