I think the inference is that automakers weren't able to respond appropriately or timely because they have contractual obligations to the the workforce.If cutting salaries is required to keep the company afloat, but that's not possible without a union negotiation, and the union has perverse incentives of some sort at play, that could cause real problems.

I'm not saying that's what happened, but it's not impossible to come up with plausible situations that could lead to the situation described. I wouldn't be so sure to immediately discount the role of a union in how well a company fares a crisis, just as I wouldn't be so sure to discount the behavior of the executives. Each company probably had its own unique mix of problems.