Why does Ariel try to instigate quarrels among the plotters? What is the result?

Ariel had a love for fun and mischief. When Caliban begged Stephano to listen to his suit, Ariel entered invisibly. Caliban repeated the story of him being subject to a tyrant who had robbed off the island from him. Ariel calls it a lie. But since no one can see him, Stephano and Caliban thought that Trinculo said that. Trinculo protested but in vain. At last, Stephano turns upon him and gave him a good beating. Trinculo however blamed it as an effect of taking too much drinks. While Ariel had fun making them quarrel, his purpose also was to weaken and disunite them, making each other ridiculous.