It's obvious they are betting heavily on automation being the future. It's risky but if it becomes true it's going to be world-shaking.
"GM has said the job cuts and plant closings will free up $6 billion in cash, but the automaker has spent $10.6 billion since 2015 buying back its own shares"
This is a direct transfer of money from workers and worker obligations (like pensions, health insurance, etc) to shareholders. This has been happening a lot lately in several industries as Wall Street demands everyone buy back shares or get punished.
Even if they waited a few more years, the optics are just really bad. Not that optics seem to matter like they used to, most companies just shamelessly do this now.
This is the part that I'm saying isn't necessarily true. The fact that they will save $6B by shutting down these factories doesn't imply that saving $6B was the reason they did it. If you're saying that the stock buyback demonstrates that they clearly had the money to keep these factories open, even in the absence of an economic case for doing so.... Well sure, but if we're talking about better contributions to global utility they could have made than the stock buyback, subsidizing unproductive factories is a horrible use of this money, compared to donating to homeless initiatives or malaria nets or any of a billion other things.
You can look at their capital expenditure though. All of their M&A, research, and investment have been in electric cars and automation.
If there weren't going for this goal they are going about it in a strange way.