/r/Place has always had massive country flags whenever it ran. But the way I see it, the largest murals need the most people working on it, and getting many people involved means having them all be connected in some way, and country-of-origin is the easiest way to do that. Combine that with the fact that the biggest non-English communities on western social media like Reddit (and Lemmy too, now) tend to be German or French, and it's no surprise that the two largest murals are those flags.
You'd wish people would find something else to represent them and have fun with things like this, but people gravitate towards the largest groups they feel a part of. Low hanging fruit, I suppose.