Instantiating camera crashes my pc

Can someone explain to me why this makes my pc crash every time ? (when I press the space key):

public class RenderScreenshot : MonoBehaviour { public int width=6000; public int height=3375;

 public string filename= "screen";
 
 private const string directory = "../../Screenshots";
 
 private int index=1;
 
 void Start () 
 {
     var directoryInfo = new DirectoryInfo(directory);
     if (!directoryInfo.Exists)
     {
         Directory.CreateDirectory(directory);
     }
     else
     {
         var fileInfos = directoryInfo.GetFiles(filename + "*.png");
         index = fileInfos.Max(fi => System.Convert.ToInt32(fi.Name.Substring(filename.Length, fi.Extension.Length - filename.Length)));
     }
 }
 
 void Update () 
 {
     if (Input.GetKeyDown(KeyCode.Space))
     {
         Camera cam = Object.Instantiate(Camera.main) as Camera;
         cam.transform.position = Camera.main.transform.position;
         cam.transform.rotation = Camera.main.transform.rotation;
         var rt = new RenderTexture(width, height, 24);
         cam.targetTexture = rt;
         Debug.Log("Camera created: "+cam);
         /*cam.Render();            
         
         RenderTexture.active = rt;            
         var screenShot = new Texture2D(width, height, TextureFormat.RGB24, false);
         screenShot.ReadPixels(new Rect (0, 0, width, height), 0, 0);               
         RenderTexture.active = null;
         DestroyImmediate (rt);
         var bytes = screenShot.EncodeToPNG();
            
         File.WriteAllBytes(Path.Combine(directory, filename+index+".png"), bytes);
         
         DestroyImmediate(cam.gameObject);*/
     }
 }

}

Note that it doesn't crash when I uncomment the part that is commented out.