Osimhen didn't outrightly reject the move to Al Hilal, he turned down offer because the salary. Currently, there's a second improved offer on the table. Also, Galatasaray is fighting to keep him, but he hasn't accepted any deal. Any news about him signing with Al Hilal or Gala is just rumors, nothing has been finalized yet. If I were to guess where he'll be playing next season, I'd say the SPL. Gala cannot match up his salary.
It's really a bad decision if he move to weaker competition for a sake of money.
He's in his prime, 26 years old, he should take a look to his friend achievement i.e. Kvaratskhelia, he won treble with PSG. Yeah Osimhen won two trophies, but it's one trophy in weak league and another one is worthless cup.
Really, in this era, many teams are lack of strikers, Osimhen with such quality can play in any team he like.