This nation was just founded and starts out with the highest-ranked rudeness in the world, this undermines a lot of nations' hard work.
I just want to know how this is possible
It is a glitch that can occur at founding. By my best guess, nations have a small chance to found without any value in a given stat, and the game's ranking system believes that this outranks any nations that do have values in that stat.
It can manually reset by mods, and it looks like that has already occurred. So everything should be good from here.