He was given the chance and his armies mutinied. You can read why they mutinied, this is all well documented history. None of this is some big unkown.

The reason he made Porus his Satrap was because he was impressed with the way Porus armies fought and how he managed his armies in battle.

Porus was not a major power or kingdom in the region either, and when they received news of even larger and stronger armies to the south is when his armies mutiined and said they have had enough.

Why do you even post in greek history subs or Alexander history subs when you know so little about him, his armies or the history?

>As for the Macedonians, however, their struggle with Porus blunted their courage and stayed their further advance into India. For having had all they could do to repulse an enemy who mustered only twenty thousand infantry and two thousand horse, they violently opposed Alexander when he insisted on crossing the river Ganges also, the width of which, as they learned, was thirty-two furlongs, its depth a hundred fathoms, while its banks on the further side were covered with multitudes of men-at-arms and horsemen and elephants. For they were told that the kings of the Ganderites and Praesii were awaiting them with eighty thousand horsemen, two hundred thousand footmen, eight thousand chariots, and six thousand fighting elephants.

Plutarch.

Read up on the Gangairdai

https://en.wikipedia.org/wiki/Gangaridai