Of course they should not be blamed. If you put yourself in their shoes their job is really tough. We shouldnt blame the because scammed projects are unpredictable. Each and everyone must do a research before joining bounties to avoid this incident.
People always need the guilty party. That's how the world works. Cryptoworld included. Bad managers who change the rules on purpose are to blame, they give crypto a bad name and ruin trust in otherwise great projects.