Not sure how re-selling material donations for the purpose to raise money is a scam. They aren't exactly misleading with this very obvious process. Clearly you don't like the optics of it, but nobody is being duped, not a scam.
A good example of where a major charity organization runs off the rails was a few decades ago with United Way. Seems like it was their CEO or maybe multiple execs got caught embezzling many millions from the coffers. I don't know how they managed to re-establish their trust with the public so quickly. That part always made me more suspicious than the embezzling did. To this day, very common for employers to push United Way on their employees, automatic payroll deductions, competitive drives with other employers / industries in a given area or region. I'm not a big fan of UW. Absolutely they do a lot of good, but it isn't as if charity organizations aren't like businesses. They can be replaced by competition. United Way seems to have some powerful, behind the scenes support system preventing an emerging equal. The embezzlement thing was powerful ugly. There was a lot of thought at the time it would destroy UW. Hardly.