Most people thought Leia Organa, Han Solo, and Luke Skywalker were legends. Like with most legends, there are fans who wrote fanfiction. Each fan has his/her own favorite pairings and headcanon. When Han (who doesn't die) and Rey bring Luke back and they defeat the Knights of Ren, people realize that the legends were true. There are some fans who see no need to get rid of their headcanons just because their favorite characters are real people. Some of these fans send in fanfics or advice to Han, Luke, and Leia. Some is friendly. Others not so much.

For example, maybe Leia gets a letter telling her to die so that Luke and Han can be together. Maybe Luke gets a letter telling him that if he were to have feelings for Leia, it would be okay because they weren't raised together. And lets not even get started on what some people think happened to Leia in Jabba the Hutt's place...