The Elephant is not OP.
The ISU is op.
BUT the elephant is OP vs the ISU. So if the ISU didn't exist the elephant would be not OP (or viewed as op, because he isn't OP).
And the Elephant is a bit usefull against IS2, and because of Company of Callins, the Elephant is often a good choice, because you neeeed him vs the OP ISU anyway.
Really? Is this your logic?
Elephant was crazy OP long before ISU. The meta was different so it was rare to see one. Why would you wait for super late call in if you could have a bunch of T3/T4 tanks roaming the field due to German armour being far superior.
Someone said you can build ZiS and counter Ele this way. Well from my experience it doesn't work because I can snipe Soviet tanks without even getting into range? You want to rush in and close the distance? Go ahead! My support is waiting for you while I'll retreat my Ele so it can still snipe your tanks from the distance.
Play something else than 3v3 from time to time to see things as they are.