Alexander and his army had been campaigning for an extended period when his generals refused to continue onwards into India. War exhaustion would be the primary motivation that prompted this event.

After initial successes against the Persian Empire in the early 330's BCE - notably the Battle of Issus, when Darius' family was captured by Macedonian forces and numerically superior Persian forces were defeated - Alexander continued his pursuit/conquests into the East. Darius was taken hostage and murdered by one of his former satraps while the Persian Empire collapsed. One could make an analogy that Darius was a sort of trophy in Alexander's eyes, and Alexander sought revenge in having his prize stolen from his grasp. This, among other factors, prompted further campaigning into Asia.

In mid-320 BCE, Alexander's army refused to continue onwards. Even though Alexander's army knew mostly victory, this period of time spanned 10-15 years, primarily filled with military campaigns and its associated hardships. Coupled with being thousands of miles from home, faced with years of travel in order to return, and only more conflict in their immediate future, Alexander's army revolted. However, one can also consider logistical matters, political concerns regarding 'allied' satraps under Alexander's flag, and other similar issues that accompany a new empire as secondary factors for this event.

My information for this stems from a course I took studying Ancient Greek history with Nathan Pilkington - utilizing Sarah B Pomeroy's "Ancient Greece: A Political, Social, and Cultural History" as the principal text-based source of information.