I guess this could be for one (or a combination) of a few reasons:
1) Gallagher is going. Would be very sad if this is the case
2) One or both of Ugochukwu/Lavia are going to be out for a long time and we want reinforcement - this very well could be the case, though I've thought of Casadei as a more attacking player than either of those two
3) We've identified the need for a midfielder who can win a header or two, and as a bonus he seems to have an eye for goal
4) Maybe Leicester are about to sign someone in his position? We've seen before how clubs prioritize their own players over loanees, and they're in a comfortable enough spot in the league to afford a slight drop in quality from a rotation CM if the incoming player is a bit behind Cesare in their development.
5) Loan rules/limits? I'm not sure what restrictions are imposed on domestic loans but if we're envisioning sending Santos back out on loan later in the season maybe we need to open up a space?
I liked a lot of what I saw from Casadei in pre-season, he's obviously raw, but so is most of our squad. I just hope that if he does get recalled we don't waste half a season by just having him sit on the bench a couple times and play dev squad games. I know he wasn't first on the teamsheet for Leicester but he's had 25 apps, adding up to over 1100 minutes, producing 3 goals and 2 assists... for context Mudryk's played fewer minutes this season.