From what I've read around, it seems that the deal fell through due to the medical check-up carried out by Juventus. It seems that the player didn't pass the medical tests, but maybe I'm wrong. I can't find the article but it seems to have said exactly this. I wouldn't be surprised if they would have increased the checks after the previous purchases.
I thought Juventus dropped out of the race to sign Sancho because of the player they signed, and they didn't have enough money to pay for Sancho's transfer fee at the moment. I have been following transfer news for a few days now, and I haven't heard that Manchester United and Juventus have agreed on a transfer fee for Sancho. How sure are you with this information?
I would have assumed Juventus was a rich team and they could have afforded, but looking at how they are just trying to slow down now, I guess they hit their limit of what they can spend. They looked like a team that can easily spend 100+ every year, because of how much money they made from a decade long domination, but these past few years who they are not doing that great cost them some money.
Hopefully, they will do a better job this season, and get a better result. Can they end up winning the title? I do not believe so, we are seeing a team that is a top four team easily, without a doubt, but the difference between 4th or 3rd, and first place, is a huge one and I am honestly not entirely sure if Juventus made that jump yet.