Why didn't the framers of the Articles include an executive branch or a federal court system?

Answer 1

Actually they did have an executive and judiciary, but they were very limited.

The President of the Continental Congress continued as the President of the Confederate Congress, but it was closer to a Prime Minister beholden to Congress before he could do anything significant, and with a very short term of office.

Judges were appointed for piracy problems and inter state disputes.

the United States were not the United Provinces. "States" is equivalent to nations or countries. The UN is the United Nations with similar limited executive and judicial powers to the Articles of Confederation.

The nearly sole purpose was to provide for mutual defense from Britain or other foreigners.

Answer 2

The only purpose of the Articles of Confederation was to legitimize a sort of league of States which had already been operating during wartime, with the major emphasis being on the rights of the States. None of the States at the time wanted a strong central government, nor a strong central executive branch or court system. 10 years later, after the war had ended and things had settled down a bit, it was recognized that something stronger was needed to manage the new growing country and so a constitutional convention was created. For this, the Masonic leaders prevalent in the early colonial Founding Fathers borrowed the ideas of another famous Mason, Montesquieu, who strongly advocated for a separation of powers and proposed the three separate branches of government that we now have.