Sometimes, I see players who lose on purpose. They deploy a Barbarian, and acknowledge defeat in a minutes. Why do they do that?

Players who wanted to lose on purpose always use this kind of strategy to take off some of their trophies to join a lower league.
They deploy a barbarian and then hit the end battle button to lose on purpose.
Once you hit the end battle button after you deployed a single troop, you will automatically lose the battle and shell out some of your trophies.
Barbarians are most commonly used because they are low cost troops.
Other players also use archers which is also a low cost troop.
Players with heroes also use either the king barbarian or the queen archer because they costs nothing to train.