Retirement tax questions

Probably not.  If he cashed out more than he needed to, he just owes the tax on it.

He may be able to contribute some of the money to a Roth IRA, since he's already paying the tax.  That would allow future withdrawals to be tax-free (and future withdrawals from a Roth are not subject to the RMD.)

Or, if he just invests the money with a mutual fund or money manager, then at least in the future he will only owe tax on the gains and not the whole amount (and gains are taxed lower than ordinary income.)