"From GM's perspective they stood to lose nothing and potentially gain. "
No, investing 2 Billion in a scam essentially ruins the credibility of many people and puts the CEO in jeopardy.
Being stupid has consequences, even if you can back out.
"The big banks, the suppliers, the big corporate entities GM has to deal with don't care "
Of course they care - you think that the suppliers of GM who give GM massive credit want to know that the company is doing something this dumb and could end up in Chapter 11 - again - where they lose their money?
There is no positive spin on this for GM it makes them look like idiots - to the point wherein the CEO should definitely be fired because this is not just 'some deal' it's an existential issue concerning their future.