Even if the firing is legal - and California does have restrictions when a company fires a large number of people at once - arguing that it's "for cause" to withhold severance packages is going to be a lot more difficult.
For the rank and file layoffs yes, you need to have a notice period and those people will probably get severance at least equal to that much pay. But C suite executives are another matter. It’s very likely that Elon Musk received access to information after taking control that supports a for cause dismissal.
