navmeshagent and rigidbody question

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.AI;

namespace Player { public class GrenadeExplosion : MonoBehaviour {

     private Collider[] hitColliders;
     public float blastRadius;
     public float explosionPower;
     public LayerMask explosionLayers;
     private Rigidbody enemyRigidBody;
     private Vector3 enemyVelocity;

     void ExplosionWork(Vector3 explosionPoint)
     {
         hitColliders = Physics.OverlapSphere(explosionPoint, blastRadius, explosionLayers);
         foreach (Collider hitCol in hitColliders)
         {
             if (hitCol.GetComponent<NavMeshAgent>() != null)
             {
                 hitCol.GetComponent<NavMeshAgent>().enabled = false;
             }
             if (hitCol.GetComponent<Rigidbody>() != null)
             {
                 hitCol.GetComponent<Rigidbody>().isKinematic = false;
                 hitCol.GetComponent<Rigidbody>().AddExplosionForce(explosionPower, explosionPoint, blastRadius, 1, ForceMode.Impulse);
                 if (hitCol.CompareTag("Enemy"))
                 {
                     enemyRigidBody = hitCol.GetComponent<Rigidbody>();
                     enemyVelocity = enemyRigidBody.velocity;
                     if (enemyVelocity == Vector3.zero)
                     {
                         Destroy(hitCol.gameObject);
                     }
                 }
             }
         }
     }

     void OnCollisionEnter(Collision col)
     {
         ExplosionWork(col.contacts[0].point);
         Destroy(gameObject);
     }

     // Use this for initialization
     void Start()
     {

     }

     // Update is called once per frame
     void Update()
     {

     }
 }

}

desired effect: enemy object is blown up into the air on collision with grenade and lands on the floor, once its stopped tumbling, its get destroyed. actual effect: enemy object is blown up on collision with grenade.

how do I implement the desired effect?