This is where it all began.
Arnold was made a Colonel and put in command of the military operation and was paired with Ethan Allen and the Green Mountain Boys, a local militia acting as irregulars in the Continental Army. Allen's militia refused to accept Arnold as their commander and threatened to leave if Allen didn't lead the operation. Although unclear, it was assumed that Arnold and Allen worked out an arrangement that kept the operation on track, although the Green Mountain Boys still refused to take Arnold's direct orders.
The operation was a success, but Allen took all the credit. A relief militia of 1,000 men was sent to hold Fort Ticonderoga with instructions that Arnold was to serve under the command of the militia leader. Arnold refused, resigned his commission, and went home.
After this, Arnold began building a reputation for engaging in disputes with the people he worked with, and the Continental Congress kept passing him over for promotion. General George Washington even wrote to the Congress on Arnold's behalf, telling them that he would lose several good officers if the Congress keeps making politically motivated promotions instead of recognizing merit.
tl;dr... Arnold kept getting passed over, kept quarreling with his peers, and saw slights against him everywhere. Feeling betrayed, he eventually turned traitor and fled to England after being discovered.
Ethan Allen is still selling overpriced furniture across the country.
-PJ
I think Ethan Allen demanded the surrender of Fort Ticonderoga “in the name of the Great Jehovah and the Continental Congress.”