The only problem with that thinking is that he is a pretty awful target man, easily bullied for a man of his size and with a lousy first touch which makes it hard for him to control the ball and play others in. His strength is in playing for an underdog when the opposition is holding a high line and he has space to run into behind. Juve will be playing week in and week out against teams that park the bus and he has nowhere near the level of technical ability needed to function in a tightly packed attacking third. This whole thing is baffling to me but dear god I would love it if we pull it off.
Maybe they think they can work on him. Belgium aren't an underdog and he bags plenty for them.
I think he's a striker who needs consistent service. He's not going to create much off his own back, but if you put him in a system where he has a clear and defined role I do believe he can work.
Then again, Juventus aren't the most creative side .. but maybe under Sarri that will change, I'm guessing they do have a plan for him. I'm hesitant to call it baffling because Dybala really was poor for them last season and simply doesn't fit in, and Lukaku's reputation at United might have plummeted but he's still a first choice striker for one of the best national sides around.
It's a good trade from United's perspective too though, if Dybala is motivated. Because that clearly hasn't been a good match either. Sometimes players just don't work at certain clubs but can flourish elsewhere.