Of course, Hummer EV turned out to be one of the most technologically advanced pickup trucks today: its own electric platform, many engines, all steerable wheels, a huge battery, and state-of-the-art equipment. But, it seems, this is exactly what played an evil joke on it - it is very difficult to produce such an electric car.
It is worth noting that competitors are manufacturing much faster. For example, the Ford F-150 Lightning electric pickup keeps the pace of about 150 units per day - here is an example of a simpler electric car. So, GMC needs to make a lot of effort to accelerate.