Am I missing something, or did they not do anything to adjust for how many Kias/Hyundais are in those cities?

That could explain why some cities saw much bigger spikes than others - or it might not! Feels sloppy.

edit: this obviously doesn't negate your point, there's clearly an enormous spike. It's just weird since the article took the time to break it down by city, and to call attention to some cities seeing larger spikes than others.