Problem with adding custom class object to a List

My problem is simple:

Script "Trigger", not attached to any gameObject, just sitting in the Assets/Resources folder.

 using UnityEngine;
 using System.Collections;
 
 public class Trigger : MonoBehaviour {
 
     public GameObject triggerObject = new GameObject();
     public string triggerType = "";
     public Coordinate coords = new Coordinate();
 }

Script "Switch", attached to a gameObject that represents a pushable button/switch.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class Switch : MonoBehaviour {
 
      public List<Trigger> onTriggers;
 
      void Start () {
           onTriggers = new List<Trigger>();
      }
 
      public void AddOnTrigger(GameObject obj) {
           Trigger newTrigger = new Trigger();
       onTriggers.Add (newTrigger);
       onTriggers[onTriggers.Count - 1].triggerObject = obj;
      }
 }

With AddOnTrigger(), I want to 1. add a new Trigger to the onTriggers List, and 2. set the triggerObject that is part of the Trigger class.

However, when the function is called, a trigger is added to the list (list size increased acordingly), but the inspector shows "None (Trigger)" in the list's fields, and the triggerObject is still null.

When I had the Trigger class locally as part of the Switch script, it worked flawlessly. What am I doing wrong?!?