“In 2016 Trump ran on ‘Lock Her Up!’”
He didn’t. It was a chant at rallies, but it never was a campaign statement by him. At the debate he did say that if he were President, she’d be in jail already.
But not a campaign promise.
At a Trump-Clinton Debate on Oct 9, 2016, Trump said to Hillary quote:
"I didn't think I'd say this, but I'm going to say it, and I hate to say it, but if I win I am going to instruct my Attorney General to get a Special Prosecutor to look into your situation because there has never been so many lies, so much deception, there has never been anything like it. And we're gonna have a Special Prosecutor."
3 minute 43 second clip of the above quote and Hillary's response: