public variable gameobject

I have done public GameObjects in many scripts no problem but for some reason this one isn't working. If I substitute the actual name of the enemy in the field the script works. but when I make the enemy a variable and drag the enemy I want into that slot I get these errors "Object reference not set to an instance of an object" As I said, when I substitute the actual enemy name the script works and disables that enemies "enemybehaviour destruct" script. The game will play and I don't get those errors until the player hits that trigger zone. this script doesn't work

   public  GameObject Enemy;
 private MonoBehaviour Attacks;

 void Start () {
     
     Attacks = GameObject.Find("Enemy").GetComponent<EnemyBehaviourDestruct>();

 }
 
 void OnTriggerEnter (Collider other) {
     if(other.tag == "Player")
     {

         Attacks.enabled = true;

     }
 }

}

this script DOES work

 private  GameObject MadScientist;
 private MonoBehaviour Attacks;

 void Start () {
     
     Attacks = GameObject.Find("MadScientist").GetComponent<EnemyBehaviourDestruct>();

 }
 
 void OnTriggerEnter (Collider other) {
     if(other.tag == "Player")
     {

         Attacks.enabled = true;

     }
 }

}