This is only partially true. It ignores the job losses that result from the fall in capital available to firms. Additionally, anyone owning equities, which should be most of the middle class although I'm aware this isn't the case, will see their wealth decrease. I'd argue that the only people who benefit from crashes are those with large amounts of cash assets, which is generally not how you should be holding your wealth. Holding cash, after all, is just withholding wealth from being productive.