The issue would have affected his performance if not that he is a player that has the determination to find his strength even at his weakest, we even thought his best will be only on Napoli but what he has proven in Galatasaray is more amazing than in Napoli, though he won some high awards in Napoli but his appearance in Turkish league was more than his Italian serie A, so just like the golden Boot he won on the Italian he would also win the same on this league with Galatasaray because he is the highest scorers of the league currently, so is a very rare award for a newcomer to win in the league he has just arrived for a year, perhaps he could have still win the next golden Boot if not for his leaving this year.
It is true that a newcomer is rarely seen as golden boot, normally not many players have their rookie season in a league and end up being the top scorer. But this is Osimhen we are talking about, dude is valued at 75 million, that is his release clause and he will be sold for 75 million eventually, this summer.
The general "a player won't be top scorer on their first year at this league" thing is not for players who worth more than most teams in the league, he is worth more than 50%+ of the clubs, and I mean entire clubs. So it wasn't really a shock to anyone who watched him play before, if he failed to score this much, it would have been problem for other players in Galatasaray to not be able to feed him well, but they did and he scored a bunch.