If you want to do Occam's razor and actually find the simple solution. Ask yourself could this just be a simple goof up?

Could he have just selected Goldberg accidentally from his contacts?

Let's find out.

First, find out who is in the principals committee

Principals Committee The Principals Committee of the National Security Council is the Cabinet-level senior interagency forum for consideration of national security policy issues. The Principals Committee is convened and chaired by the national security advisor. The regular attendees of the Principals Committee are the secretary of state, the secretary of the treasury, the secretary of defense, the attorney general, the secretary of energy, the secretary of homeland security, the White House chief of staff, the director of national intelligence, the chairman of the Joint Chiefs of Staff, the director of the Central Intelligence Agency, the homeland security advisor, and the United States ambassador to the United Nations.

Then find out who was not on the group text.

Does this person who is not on this group text have a name that would be next to Goldberg in your contacts list? A name you could easily select by accident?

Find someone like that and you found out how Waltz screwed up.

That's a simple explanation. That is Occam's razor.

And yes I did do this exercise and yes the name fits