The moving Rocks remain a mystery till date.
The explanations offer include
they are moved by the wind
“This is the favorite explanation. The prevailing winds that blow across Racetrack Playa travel from southwest to northeast. Most of the rock trails are parallel to this direction. This is strong evidence that wind is the prime mover or at least involved with the motion of the rocks.
Strong wind gusts are thought to nudge the rocks into motion. Once the rock begins to move a wind of much lower velocity can keep the rock in motion as it slides across the soft and very slippery mud. Curves in the rock trails are explained by shifts in wind direction or in how the wind interacts with an irregularly shaped rock.”
There are places in the world that have stronger winds and no such movement of Rocks are reported from there.
moved by Ice
“A few people have reported seeing Racetrack Playa covered by a thin layer of ice. One idea is that water freezes around the rocks and then wind, blowing across the top of the ice, drags the ice sheet with its embedded rocks across the surface of the playa.
Some researchers have found highly congruent trails on multiple rocks that strongly support this movement theory. However, the transport of a large ice sheet might be expected to mark the playa surface in other ways – these marks have not been found.
Other researchers experimented with stakes that would be disturbed by ice sheets. The rocks moved without disturbing the stakes. The evidence for ice-sheet transport is not consistent.”
This also does not wash as there are more places with the same condition and no report of Rock movements.
We may add this to the list of things we do not understand.