You know, I'm starting to notice that people who throw insults or defamation at someone tend to project their true selves onto them. So when a girl calls a guy an idiot in manga, they're really calling themselves an idiot ... which is true in a lot of cases, and this one is no exception.
The childhood friend is just as much of an idiot for not snagging MC earlier before a complicated arranged marriage took him away, as are many other losing childhood friends who took too long to make a move, and/or are just too toxic to them and not take accountability for their treatment towards them.