I know that the others weren't of the same age, but the reason I mention other age gap relationships is more the focus on her old age, while the other way round things do not get so intensely debated in the media (except for really famous people), about what is or could be physically wrong with the older partner or about her/his "fading beauty" etc.
Another aspect I mean is that much more money or power are also "position of authority" over someone, same as being much older and experienced. Sometimes all three aspects go together. But to say the age gap is much more despicable than an income difference of several millions, I'm not so sure it's that clear cut.
Carrie and Boris Johnson are another example of a couple with an age gap.
I agree that the clip from the plane looks very strange and not like banter, but there are so many comments here bashing Ms Macron's age in itself, apart from the meeting time of the couple.
About how they got together, same as other PP, I read during the time of the election of his first presidency similar articles of that they met at the theater group and he was obviously infatuated, but that this did not become a real relationship until later, and, as others said, that his parents sent him to a different school. I don't know what the truth his here, of course, but I don't think it's so clear they were having a physical relationship with him at 15 years. I understand the grooming aspect that others mentioned, though.