Looks chaotic, is usually rehearsed
A midfield that constantly swaps positions during a passage of play can look improvised to a casual viewer, but the movement is typically built on a rehearsed structure rather than spontaneous creativity. The purpose is to disrupt an opponent's marking assignments: if a defender is told to track a specific player, that job becomes far harder when the player in question keeps changing zones, and the defending team is forced to choose between following an individual across the pitch or handing responsibility over to a teammate mid-phase, both of which create brief moments of confusion an attack can exploit.
The covering rule underneath it
For rotation to work without leaving gaps, teams generally operate a covering principle: whoever vacates a zone is trusted to be replaced immediately by a teammate, so the structure of the team's shape survives even as the individuals occupying it change constantly. This is why rotation looks fluid rather than reckless when it is well drilled, and why it can look disastrous when a team lacks the discipline to fill the vacated space, leaving gaps that a well-organised opponent can exploit the moment possession changes.
The trust it requires
Because rotation depends on a teammate reliably filling a vacated zone, it requires a level of technical trust that takes time to build, which is one reason settled squads with long-serving midfield partnerships tend to rotate more convincingly than newly assembled ones. It is not simply a tactic that can be instructed in a single training session; it depends on players developing a shared, largely unspoken sense of where the others will be, which explains why the most fluid midfields in the game are usually also among the most experienced together.