This could easily be a science fiction story, as we don't know who the goddess really is. She could just be an alien lifeform with advanced technology who is subjugating a less advanced lifeform. That cave could be an entrance to a ship and it self destructed on her death. There is only light detail on many items in the story, so it could go in any direction.
The three soldiers may have been sent on purpose by a crafty general to do exactly what they did. The general may have despised the corruption in the system and set about training and tempering her armies so that the three soldiers to be the best rose to the top. Then the general could have exploited the corruption to have these soldiers sent as a sacrifice, in the hopes they would do their job, which has been ingrained in them. We don't know the general and only get to know her from the soldier point of view. There is a lot of room left to the imagination.
The story was a fun listen as we don't know everything, but get enough details to make us want more. I want more from this world, and I want to see if the goddess does come back in the future. The next 43 years sure will be an interesting period. Was the city set up on the goddess's power, or did her powers merely destroy what they could? Where is the general and did she survive? There is a lot of meat to chew on.