Over a year's period, the cost of the battery for the Bolt will decrease between $500 and $1000 based on lithium battery costs dropping at a rate of 5-10% depending on who you ask. They can have the car out now, get the halo effect, and eat a couple of grand on the front end while recouping on ZEV and CAFE compliance on the back end. Maybe they can prevent some Tesla fanboys from being born, as people tend to protect a brand while owning it, in order to safe face, even if they do a 180* after trading it for something new.
I've not worked for GM directly, but a subsidiary, and GM is very... segmented. While some segments may support EVs, there are groups within GM that want nothing more than to see all BEVs die. Remember, you have a lot of engineers, managers, etc, who all have their paycheck riding on ICE vehicles. These people are the types who are only concerned with their well being, and not the well being of the company.
Lastly, GM won't push BEV tech until they can make a substantial profit on it. Right now their profit comes from gas guzzling SUVs and trucks, so that's what they push. The only reason GM sells cars these days, especially small fuel efficient cars, is to keep their CAFE compliance in check. It was common for GM to take a $1,000 to $2,000 loss on fuel efficient vehicles just to sell enough to keep the CAFE numbers high enough to keep selling the SUVs. (Instead of investing the $$ to make those SUVs more efficient. A serial hybrid SUV could easily get the numbers they need, but because of the segmenting, the managers in charge of the SUV programs won't do that unless they're forced by the upper executive board.)
GM is the example of what happens when you have a bunch of divisions just trying to save their own hindquarters instead of having a company that's driven by vision. (Think Apple with Jobs, and Tesla with Musk.) It's truly amazing what a company can accomplish when they have leadership with a goal and purpose.