If OpenAI didn't have adequate safeguards, either through negligence or becauase it was in fact being run deliberately as a fraudulent charity, that's a particular failure of OpenAI, not a “well, 501c3’s inherently don't have safeguard” thing.
Most people just tend to go about it more intelligently than Trump but "charitable" or "non-profit" doesn't mean the organization exists to enrich the commons rather than the moneyed interests it represents.