Even if it’s true, it’s just a traffic violation at best. Or maybe charge Trump for driving without a license. That’s the “criminality”?
From a purely legal standpoint if the story were true, and it apparently isn't, there were very serious crimes committed at that moment by the driver and anyone involved with their decision.
Just like it would be illegal for an Uber driver to refuse to take you to your destination and instead take you to a place of their choosing, something generally treated as kidnapping, it is even more illegal for a driver acting in concert with other government employees to effectively detain the president while he is involved in his presidential duties.
Preventing the president of the United States, and our Commander in Chief from going to the Capitol Building if he wanted to do so, and then effectively detaining the president of the United States by taking him elsewhere results in a series of very serious crimes by the people involved. At the very top is the same charge brought against some of the protestors - interfering in the operations of the government. That's a felony with a long prison term attached to it.
And then we have things like kidnapping a federal employee, because the President is also a federal employee. And sedition, and possibly treason, and conspiracy to do all of those things.
Just imagine the charges that the DOJ would bring if some random person managed to take off in the presidential limousine with the president in the back seat and said they were taking the president to some location other than where he wanted to go.
Detaining government officials is what happens in a coup. If the testimony is true the January 6th committee just showed that on January 6th members of the Secret Service participated in a raft of illegal activities, all of them felonies, and engaged in an extreme breach of our political process.
Of course what really happened is that some foolish young person told a wild story to try to get their face in the media for their 15 minutes of fame. Secret Service agents are too smart to let themselves end up in prison for the next 20 years.