Isn't it obvious? Because we believe we've found in him, as in others who were also put on huge & multi-year contracts, someone who will sort out a specific role on the pitch (or in the squad) for the next decade. It goes hand-in-hand with the desire to also find a manager who will stay put for the next quarter of the century.
It's a noble idea when you know what you're doing. But with the guys that kept the likes of Phil Jones and Jesse Lingard around for what seems like forever, probably because the great man had a few good words to say for them, ... i'm not so sure. I mean, there were reports from Germany that Sancho's a bit of a slow starter who often starts pre-season a little overweight and then plays himself into rhythm. Of course, he was afforded that luxury in an inferior league and at a club that can finish 30 points behind Bayern Munich and still have a good season. Furthermore, a club which had chosen to overlook his shortcomings, as long as Sancho kept racking up the numbers, with the goal of finding a potential buyer. And, God, they are good at selling. The big question is, are we clever buyers? We got dazzled by his good stats and the fact that he links well with players around him. The latter is the only thing that distinguished from Rashford and Greenwood at the time. They all live and breathe for the ball in-behind. When that's not available, the other two will start shooting from anywhere, Sancho will look for the one-two and the potential cut-back. We need "heavy lifters" in the final third, players able to keep the ball and make good decisions in tight spaces and with limited time to think, players who don't shy away from challenges and their influence doesn't evaporate as soon as they find themselves away from the box. What we did, instead, was keep hoarding attackers who mostly rely on others to do the hard work for them. But that's not the way to play football. That's the way to empty your midfield of any creativity and make McFred a mainstay in the midfield to make up for the general effort that's lacking ahead. In hindsight, it really looks like watching a car crash in slow motion, doesn't it?
Nevertheless, i believe there's a good player in there. Not an 80 million/ 350 thousand pounds p/w player, but a good footballer still. And we put ourselves in a position where we have to get something out of him. It's just that he's case was poorly handled. It's a shame, too, in some ways, because he's trying to play himself into form outside his natural game. He was never the great dribbler who would draw defenders and constantly beat them to create openings. But without Martial and with Bruno trying to be as direct as possible, someone has to make things happen when the ball in-behind isn't an option. He can certainly play better than what we're watching right now.
In the end, it's a mix of arrogance and incompetence by the club. Gary Neville said a right thing in his altercation with Roy Keane the other day. As strange as it may sound, trading goals and assists (end product) for different qualities in some areas in the attacking third can lead to a better team. It's amazing that, at United, someone has to spell it out to the decisions makers.