Question

How did a weak national government lead to the conditions at valley forge​

Answer 1

It was the time when there was a weak federal government and the states were rendered with more powers than the Union government. Valley Forge is the third military camp which was set near Philadelphia.  

George Washington led the continental army and he chose that specific place due to the strategic benefit that he could keep an eye on the British army which was stationed there. Americans built log huts in order to protect themselves but unfortunately before the commencement of the battle, American troops confronted deficiency of food and ammunition supply and many soldiers died being impoverished.  

This was due to the sheer laxity of the continental congress which did not have command to govern the army during the war.