What the heck are you talking about 0_o
Why high rank 4 player play FFA like teaming ?

Learn to give combinations with your opposite and take the most points you can, every one is agreeing to check mated the laterals first.

It is a variation of the 4pc (Four players chess). There is solo, FFA (Free for All) and teams
https://www.chess.com/4-player-chess?g=8080168

Imagine an abondoned remote island in which my tripe and your tripe and two other tripes are competting for resources, so, clash between them is a must.
There is nothing in common that would make these 4 tripes settle in peace, except the fact that my tripe can attack the other two tripes directly, just as your tripe do.
So, since me and you on the opposite sides, and cant attack each other immediatly, why dont we form short term coalation, and settle our issues later. At least after eleminating one of the others.
This tendancy of coalation is also propagated by the the way ffa rating system works. In short, one of the players must be eleminated to avoid losing the maximum lose of the rating points.
The confusion starts when the players are 3, where you never know who will attack who. This depends on your emotional intellegence, logic and calculations, although you will never be 100% accurate.
Yep I'm a 2200+ FFA player.Almost ranked game (2000+) everyone start play teaming and attack the unlucky guys =))))) Omg It is due I don't understand the meta of the game or they are taking advantage of team ups to climb the ranks.That's why I play a lot of games and can't get past 2400 elo.Chess com has team mode but They don't play it
P/s: I've noticed that they often team up against each other while playing anonymously against each other