From what I understand ppl say this Bcuz he came and fought Porus and then went back. Which was unlike him. So I have heard many Indian ppl saying that he was defeated either by Porus or by Chandra gupta ( ppl differ on who defeated him ) and that’s the reason he went back and the fact that his army revolted was just a lie made by the Macedonians. Also they bring up the crossing of gadrozia and say that if he was just going back why would he go from such a inhospitable wasteland rather then the sea or other roads, and he prob. Took that way when he tried to escape from india after his defeat. That’s all I understand
More can of course be said, particularly regarding the march in Gedrosia, but I discuss what the sources say on Alexander's closing of the Indian campaign here. Put simply, half of our source tradition on Alexander runs the gamut from cynical to openly hostile, and if Alexander had somehow lost the Battle of the Hydaspes against Poros – or somehow Chandragupta, who was not even king of anything at the time – then we would expect at least one of the surviving accounts to have said it.