I'm not going to act like this is that surprising. Immanuel Quickley was the most improved player in the country this past season and arguably the most clutch player in America. He turned himself into SEC Player of the Year and a Third Team All-American. His stock was never going to be higher, he got better defensively and he played himself into an early 2nd round, maybe a late 1st round pick.
But there were rumors that he may stay for a junior year. Could he play himself into a lock 1st round pick? That was ultimately the question. There are also stories of how much his family values getting an education (he still can obviously get a degree from Kentucky for free as he plays pro thanks to the scholarship). Then there was this video from the national title day:
Don't get me wrong, Kentucky is still going to be a preseason top-10 team next year. But Quickley was going to be the perfect returning guy for this roster. They have a bunch of high-quality wings including top-5 recruit Terrence Clarke. They have Devin Askew coming in (he reclassified) and feels a bit like Quickley in the sense of it will take him a year to adapt to the college game. Quickley could play on or off the ball while shooting 40% from three. That's where it was important for him to come back. Be that lead guard if Askew struggled to start. Now they are relying on a grad transfer in Davion Mintz to be that until Askew can adapt to the college game.