Why doesn't Unity attach a gameobject in the custom inspector field?

Question

Unity

In the class file for which the editor script is written, a two-dimensional array of gameobjects is declared:
public GameObject[][] blocks;
The script for the editor itself

using GameLayer.GameManagers;
using UnityEditor;
using UnityEngine;

namespace Editor
{
    [CustomEditor(typeof(LevelGameManager))]
    public class LevelGameManagerEditor : UnityEditor.Editor
    {
        private int rows, columns;
        
        public override void OnInspectorGUI()
        {
            DrawDefaultInspector();
            
            EditorGUILayout.Space(30);
            
            LevelGameManager myTarget = target as LevelGameManager;

            EditorGUILayout.LabelField("Blocks");
            rows = EditorGUILayout.IntField("Rows count", rows);
            columns = EditorGUILayout.IntField("Columns count", columns);
            
            myTarget.blocks = new GameObject[rows][];
            
            for (int i = 0; i < rows; i++)
            {
                EditorGUILayout.LabelField($"Row {i + 1}");
                myTarget.blocks[i] = new GameObject[columns];
                
                for(int j = 0; j < columns; j++)
                {
                    myTarget.blocks[i][j] = (GameObject) EditorGUILayout.ObjectField($"Column {j + 1}", myTarget.blocks[i][j], typeof(GameObject), true);
                }
            }
        }
    }
}

The problem is that Unity, although it displays a list of project gameobjects, does not want to attach and "remember" that you dragged something into it.

How to fix it?