Neither Clinton nor Biden has been indicted. Clinton has, of course, been investigated about a thousand times, and nobody ever found anything.
Trump is an idiot. And the people testifying against him will be his own staffers, attorneys, and more. All his life, he's believed he could do anything he wanted, and then, if necessary, talk his way out of any consequent problems. While it didn't entirely protect him from business disasters, it did keep him out of prison.
But now it's time to pay the piper.