>At the very least they are getting an aesthetically pleasing exterior design and a ready email list of potential buyers.
Is a pickup truck exterior design and a customer list worth the 3 billion in market cap that GM lost since the news broke?
GM may not take a monetary damage from dealing with Nikola, but they will still suffer a reputation damage. If and when Nikola folds, GM's management will be seen as hilariously incompetent for not doing the proper due diligence, and the market will price that in accordingly.