Billionaires are allowed to have their cake and eat it too in the form of loans backed by their stock holdings. This is how they get to have $500MM yachts without having to actually sell their stock and lose control of their companies. It's how they pay themselves without having to pay taxes, because it's treated like debt and not income. Treating these like capital gains would be a start.
It's less what should he have done, than what shouldn't he have done. Specifically, he pushed conspiracy theories, demonized his health experts, and touted ineffective cures, and ultimately cast doubt on the safety of the vaccines. All to pander to his base. He had a remarkable chance to build trust in government via a truly extraordinary vaccine rollout, to a crowd which is historically distrustful. Instead he squandered that goodwill on petty fights and self aggrandizement.