What are the biggest differences between DeShaun Watson (the player) in Houston and now in Cleveland?

This guy was on track to be in the Mahomes/Burrow/Hurts/etc wave of Next Great QBs in the league when he was in Houston. He was a dual threat QB who consistently made big plays with his arm plus had the threat of being able to run.

Obviously he went through all the off-field stuff and had to sit out a year+ … but now he just seems like a shell of his former self. Can anyone who really studied him in Houston and now has followed him in Cleveland pinpoint why?

• Is it rust?
• Is it the new system?
• Is it the supporting cast (this one seems unlikely)?
• Was he actually not that great in the first place?

I'm just confused. I figured by now we'd start to see some of the old Deshaun. Instead, he's just a very below average QB who plays without much joy or enthusiasm.

Thanks for any insight.