That’s not the issue. Rebellion is a company that makes and sells games. Those customers bought from a third party reseller, that had stolen keys, and that did not send any of those sales to either Rebellion or Valve.
Giving away hundreds, maybe thousands of copies, could hurt the company. It’s 100% the vendors fault and responsibility, not Valve or Rebellion’s.
Also, yes I do understand that it must really suck for these customers, but when you buy anything (a game, software, whatever) from a third party rather than the person who has rights to sell it, these things can happen.