What events led to british defeat at saratoga

If I remember, General Burgoyne of the British army was supposed to meet General Howe (British) and Lt. Colonel Barry St. Leger (British). Burgoyne's plan however failed. Instead of meeting in Albany, Howe went on to Philadelphia and won the Battle of Brandywine which allowed him control of Philadelphia. St. Leger wanted to fight the Americans so he made an alliance with some Iroquois Indians, their leader Joseph Brant (Thayendanega), and formed Fort Stanwix. Benedict Arnold who was seeing this devised a plan where he captured a Loyalist and some Iroquois Indians and spread a rumor that his army was very large. When message reached St. Leger, he retreated immediately to Fort Oswego. Therefore, no one was left to rendezvous with Burgoyne.  Burgoyne's march alone up to Saratoga was slow and he would even throw parties along the way. He also got attacked by rebel sympathizers often. By the time he reached Saratoga, Burgoyne's army was drained and tired and in desperate need of supplies which all contributed to the British defeat at Saratoga. hope this helped :)