Why is limiting friction greater than dynamic friction?

Limiting friction is the maximum static friction which comes into play when the body is just at the point of motion.
Dynamic friction is the friction that comes into play when the body is in motion.
When the body is at rest, the cavities of two bodies are fully interlocked and we require large force to overcome the cavities.
Once the sliding has begun, the two surfaces have not sufficient time to fully settle down and hence cavities will not fully interlock and we require lesser force to keep the body in motion.
Therefore, dynamic friction is less than static friction.