I would guess possibly a couple reasons ... 1) The first 3 years in baseball you make peanuts relatively speaking . If good your arbitration years may start out a couple million dollars and then move up some for the next 3 years . By signing , Chourio is getting $10M per year right from the get go . He already has $20M in the bank for 2024 & 2025 . 2) The injury factor.. If he dives for a ball and screws up his shoulder requiring rotator surgery and or torn knee ligaments , bone fractures , he may never be the same player long term. So the long term 8 year deal is guaranteed $10M average per year ($80M ) regardless of your health . That certainly factors in.
PS The club also has 2 option years for years 9 & 10 where Chourio's total goes to $142 M for all the years. Brewers can buy him out for $2M if they don't want him then .
Even if they do the 2 option years and keep him til 2033 , 8 years from this season the kid will still be just 29 years old . He can leave the Brewers and probably still get a lucrative deal for several years then . age 29 would be still at the end of his prime years ..