Why are the presidents on mount rushmore not in order?

Because they're put there according to their role of preserving the Republic and expanding their territory ;)

The image of Thomas Jefferson was originally intended to appear in the area at Washington's right, but after the work there was begun, the rock was found to be unsuitable, so the work on the Jefferson figure was dynamited, and a new figure was sculpted to Washington's left. In 1933, the National Park Service took Mount Rushmore under its jurisdiction. Engineer Julian Spotts helped with the project by improving its infrastructure. For example, he had the tram upgraded so that it could reach the top of Mount Rushmore for the ease of workers. By July 4, 1934, Washington's face had been completed and was dedicated. The face of Thomas Jefferson was dedicated in 1936, and the face of Abraham Lincoln was dedicated on September 17, 1937. In 1937, a bill was introduced in Congress to add the head of civil-rights leader Susan B. Anthony, but a rider was passed on an appropriations bill requiring that federal funds be used to finish only those heads that had already been started at that time. In 1939, the face of Theodore Roosevelt was dedicated.