This kind of proves the thesis. EV is a hobby for the legacy guys that competes with much more powerful (by revenue) business units in the company. It's like expecting Kodak to compete and win with their own digital camera.
Tesla on the other hand, lives and dies by its EV performance, and their approach to the market at higher end kept them alive along with loans from US with few strings attached (for various reasons).
Tesla did not "break through" any thing. If any thing, existence of BoltEV and Volt does demonstrate couple of things, a legacy car company when there are profits are going to turn on dime and make shit ton of EVs, if that is what market wants.
Tesla has brand recognition behind it, but again as some one pointed out when the market for EVs in high demand and profitable, from BMW to GM, you will have them roll EVs in millions.