A love triangle in a short drama usually looks like this: the heroine is caught between the man she thinks she should want and the man she actually does. One is often the safe choice, a childhood friend or a patient doctor, and the other is the difficult one, a cold heir or a former husband who wants her back. Sometimes the triangle flips, with two women competing for the hero and one of them lying to get him.
Viewers stay for the pull in both directions. Each episode can tilt the balance, with a rescue for one rival and a jealous outburst from the other, and comment sections split into camps. The format also leans hard on misunderstandings, like a photo taken out of context or a confession overheard halfway through, which keep the heroine from simply choosing.
The weak ones make the outcome obvious from the first scene. The second love interest has no real appeal, or turns villainous overnight so the story can dispose of him. Better triangles give both rivals genuine reasons to be chosen and let the heroine make a decision rather than having it made for her by a plot twist. When the losing side gets a dignified exit instead of a humiliation, the ending tends to land much better.