Elon told him (being careful to not use any big words) that slashing income taxes on corporations and the wealthy would force massive government borrowing, so now he wants a blank check to do that. And of course, interest rates will spike as a result, driving up inflation...but he'll blame that on Biden.
This is where the Boilerboobs and Millerscums of the world rail against government spending but never say anything about choking off revenue. It's like a MAGA goober yelling at his wife for paying the electric bill just after he quits his job.