When GM started Volt development in about 2006, sedans were still popular and the Toyota Prius was selling relatively well. So I think GM just failed to anticipate the market shift.
About 20 years ago, the classic The Innovator's Dilemma came out. Included was a chapter based on a report the author had done for the auto industry back in the 1990s. On existing technology curves he found that mass market electric cars for the American model should become commercially viable around 2020, and in the next several years after that would become dominant. Until then it was a bad business to be in, and after that success was imperative for any car manufacturer that wants to remain in business.
The same author in that book and its follow-up The Innovator's Solution said that conventional car manufacturers would come up with hybrid cars first, but that route would lose to fully electric. Exactly how sailing ship companies came up with hybrid steam/sailing ships (go under steam for short trips, and you have sails if you run out of coal on a long trip), but all manufacturers who invested in that lost.
GM's actions show that they understood a lot of the message of those books. They worked on hybrid cars once that was commercially feasible, and put in the effort to figure out how to make good electric cars. They did this knowing that the technology wasn't yet commercially viable. They have declared that their future is electric only, and are explicitly avoiding committing to the tempting hybrid mistake.
That said, it remains to be seen whether they are committing another mistake pointed out in The Innovator's Solution. Which is that they are trying to make the switch without doing it as a spinoff, without separating the companies, and trying to leverage existing dealer networks. Which opens them to the problem that dealers have come to expect maintenance costs as a big part of their profit model, and therefore will try to steer customers away from electric, or will try to charge extra to stay in business. If GM can't resolve this conflict, they will fail.
Fracking may have semi-permanently put a cap on the cost of oil, which is horrific from a global warming standpoint but does seem to have altered what cars most people purchase.