Not sure whether Antoine Griezmann and Giroud are going to welcome this decision, but Mbappé completely deserves this. He was exceptional during Qatar 2022. And he represents the future for France. What is the point in making someone in their mid-30s the captain? In that case after a few years, again they need to search for the new captain. In case of Mbappé, he is already captaining a very high-quality side (Paris Saint-Germain F.C.). Captaining the French national team is not going to be too much of a challenge for him.
The leadership of team shouldn't be based on only skills or on the pitch performance. Leadership requires some outstanding qualities such as patience, courage, team playing and tolerance. I think Mbappe lacks most of these leadership skills. It is possible that he can learn on the job but for me he is not matured for the headship of the French team. Sometimes he behaves very childish and selfish.
But in terms of influence, Mbappe has it. The striker is one of the best players in the world.He could use his influence to intimidate match officials and make them favor the French team. But I hope other older player will be humble enough to respect him. There is a possibility that there might be division in the French team if he is not effective.