Why single out Bezos, who owns about 9% or 10% of Amazon rather than the owners (including institutional shareholders) of the other 90% of the business, who have presumably seen the value of their shares grow by the same amount?
I'm a bit unsure about the wisdom of connecting share value with employees' pay and conditions, since the company's share value isn't something that can readily be converted into cash to pay the workforce, at least not as a long-term plan -- share value is not the same as money in the bank, any more than is the value of your house until you come to sell it.
There's plenty for which to attack Amazon as a business, but I'm not sure this is a particularly sound line of attack -- the decision to end double-overtime and hazard pay would have been a bad one regardless of Amazon's share value, and, had the circumstances been different, the argument "We had to end the programme because the fact our shares were falling meant we could no longer afford it" would have been spectacularly wrong.