Just compare both of them during that season:
Isak: 41 matches, 10 G 3 A, 2800 minutes played, market value 30m
Nunez: 41 matches, 34 G 4 A (6 of them in the CL, 3 in the playoffs, 2 against Liverpool so Klopp saw him live), 2800 minutes played, market value 55m
Even if you say Nunez scored them in the weaker league, he was still the hotter target without any doubt in the summer 2022 after that season. Newcastle paid more than twice his market value for Isak, because they were desperate to build a team and money was secondary. I don't know any club who values money, who would have paid 70m for Isak after his 21/22 season at Sociedad.