Question

how was alexander able to turn Porus elephant into some kind of weopan?

Answer 1

Alexander launched his whole troops at night. He was continuously fighting against Porus. So this time Porus' troops got mixed up. The wild beasts(elephants) were stampeding on  the cavalry killing the king's relatives, friends etc. It made Porus weak and the massive weapon of his turned against him because his sense of security decreased when Alexander's troop didn't attack for many days.