Note how the rails show high levels of deformation whilst the surrounding ground shows comparatively little. Notice also how the big kink on the left side has pushed the ballast aside and into the track side ditch This has happened on the right side too, but to a lesser extent. The right side bend nearest the camera has pushed the ballast towards the camera.
The compression on the very strong railway line was accommodated when a weak point was found, leading to a comparatively rapid deformation to form the main buckle on the left. This then concentrated stress on both sides of the buckle, allowing the other (right side) bends to form. Can anyone who knows more on this topic comment further?