I agree that he’s not particularly trustworthy but what would be his motivation for lying here? I can’t come up with any.
(to be clear, I don't believe that, and also see no reason he'd be lying. That doesn't mean there isn't one though - and he could also be lying for no reason)
His donations became a political hot potato so maybe they’re like “look, man, my hands are tied here so maybe if you can deflect some of this heat we can work something out.” Voila, millions of untraceable donations to the republicans.