The Crusade (autumn, winter 2013-14)

I was somehow sure that the places change, for example, 7th place in the first group drops to the third group, 1st place in the 5th group goes to the second group, and so on. But if it's like this, then a person who takes 7th place in the 1st group ends up in the 5th group and presumably kills everyone there, which isn't interesting for him or the opponents, right?

No, for the sake of the game, it's best to have groups with both even and mixed compositions at the same time.
If you only create mixed groups, the result is predictable in favor of the strongest player. And if you only create groups of equal strength, they stagnate in their development because they only play against each other.

Let's say a person played poorly in the 1st group, took 7th place, dropped to the 5th-6th group, and quickly climbed back up. And it's interesting for newcomers to play with a stronger player and gain experience.