If you, the civilian, donates to a legitimate cause, the billion dollar company won’t be able to claim that donation on their tax deductions.
If they donate, it’s a zero sum game. Maybe 5 mins in the spotlight for alturism.
But if you give them the money to donate on your behalf? They don’t spend a cent and are able to get tax deductions for “philanthropy”. It’s the best possible outcome (for the company).