As I have mentioned, the Red Rock Escarpment is an actual fault line. Looking closely at the photos you can see a diagonal slope at the base of each mountain. The slope likely consists of all of the rock that has fallen from high up for hundreds of thousands of years if not far longer.
These mountains must have been far higher millennia ago. Plate Tectonics have transformed this area into what you see today, it was once a part of a very large and shallow sea over 200 million years ago which is why people find fossils from the sea in the Mojave Desert today!