for a coach like Cal who lives and dies on recruiting (take that to mean what you will about his prowess when it comes to Xs and Os), he has to get the best guys. And right now the best guys follow the $$$.
Arkansas has a little over $5Million in their NIL collective per year for hoops. That includes significant donations from Walmart and Tyson. By comparison, UK had almost nothing in their NIL collective just a year ago. Cal had been fighting with the UK AD to make major strides in NIL but they've been lax to do it, many think because UK felt they had a history that recruits would be drawn to more than $$$. Probably not a good long term way to go.
So Cal is gone. And honestly, it's a win win. UK doesn't have to pay him a huge buyout to get rid of him (which they wanted to do); Arkansas gets a bump to their program.