It wasn't complicated. The reason was that the stationmaster had used connections when hiring people to build the tracks. The tracks developed problems just days after they were completed, but the stationmaster didn't dare make the real reason public. As it happened, there weren't many trains scheduled to use that route, so after temporarily closing the tracks, he announced internally that they were undergoing routine reinforcement and sent another crew to make repairs.
In reality, the section of track that ran through the tunnel wasn't the only thing that had problems—the tunnel did, too. The workers responsible for clearing and maintaining it reported the issue, but after sending a "professional" to inspect it, the stationmaster replaced them with another crew.
The new crew belonged to a small company and lacked experience. They failed to notice the problems inside the tunnel and ended up crushing three people to death. The six people lying on the tracks were relatives of those three.
But the incident was covered up quite cleverly. The three deaths were ultimately classified as "accidental." Supposedly, the relevant authorities issued a report stating that the three had drowned and had only broken bones and deformed bodies because they'd accidentally struck rocks at the bottom of the river.
Then another earthquake split the ground open, conveniently solving the stationmaster's problem.
Leaving aside how illogical the whole thing was, that was why the six people had lain down on the tracks.
They knew their relatives had gone into the tunnel and met with an accident, but they couldn't prove it. Their police reports went nowhere, and after repeatedly going to the homes of the people in charge, they ended up being detained for several days on charges of "harassment."
The public's mouthpiece seemed to have gone silent, and nobody was willing