Burst layoffs to polish up earnings reports are “fine” (in terms of stocks), but hemorrhaging workers when your company is already in hot water for product quality complaints smells of “We’re really desperate to make our reports not look devastating”. From a stupid monkey brain point of view, it sounds like they’re throwing sailors overboard to avoid sinking and I wouldn’t want to be a passenger and risk being next, so I’d try to sell what shares I have before they’re worthless.
I don’t know what heuristics professional traders go with, but I imagine they would follow a more complex and nuanced logic along those same lines. Either way, if enough people do that, it compounds.