Last season's poor performance had several issues, one of which was the increasing number of injuries. Meanwhile, Mbappe arrival also created a different impression, as Vinicius seemed to be no longer performing well. However, people forget that Vinicius simply provided an opportunity for Mbappe to score more goals and adapt quickly. Had Mbappe not arrived at Madrid, Vinicius would still have been known as a great player last season.
I don't know if some players are having a negative impact on Real Madrid. The team had a lot of potential to improve after Mbappé joined Real Madrid but instead it has been the opposite which is attributed to the internal conflict in the team. Mbappé is scoring goals regularly but Vinícius is not doing better and he should be playing better football. Star players like Rodrygo and Bellingham are not performing to their potential. Injuries to some of the best defensive players and the absence of coordination within the team have only reinforced the gossip of infighting within the team.
Simply put, Vinicius has started playing as a midfielder to allow, as you say, Mbappe to score more goals, who apparently seems to be increasingly playing as the first lady within the team, and that doesn't surprise me given that he did the same thing at Paris Saint-Germain.