Lets look at the some of the facts
1. Demanded out of the thunder because he didn't want to play second fiddle to Westbrook and Durant after their finals loss to Miami. Was offered a very good contract to return but chose to flee to be the main alpha of the team via a trade when he rejected the contract.
2. After realising he wasn't getting a ring from the Rockets, demanded a trade to form a new super team with KD & Kyrie - didn't turn up to pre season at Houston, once he turned up at the Rockets was overweight and not very helpful to force the trade.
3. Once things weren't going his way at the nets, again demanded a trade to a preferred contender team to get his wishes.
This is 3 instances of him forcing his way off teams mid contract.
Fact is, he isn't getting any younger, he isnt the same player he was when Morey was at the Rockets with him, and the assets they gave away have made one of their rivals so much stronger than what he has made the sixers. Sure, the sixers were getting zero output from Simmons, but trading Curry and Drummond plus two first rounders really strengthens the Nets more than it does the sixers. The Nets now have a much better defence cause lets face it, Harden plays **** all D at the best of times whereas Simmons can guard 1 to 5 with ease at an elite level, another big to help them out at the centre position where they are weak, have a sharp shooter in Curry on the wings, and Simmons has absolutely no pressure to score cause KD and Kyrie do that for you.