This could have been solved by wiring the power lines of the working external usb charger to a hacked up plug and the data lines back to the PC. They even sell premade cables for this usecase where you have a car with android auto, but the car's USB port is incapable of delivering net+ power to the phone.
I was thinking the same. Also, I would have liked if they discussed/measured the worst-case power draw of the device before starting to add capacitors, as it's possible a PC USB port just doesn't supply enough current to power it at steady state.
