Keeping track of a video game mythology is hard. Like really, impossibly hard. Harder than a film or book, and why? Because the average game runtime stretches into the tens of hours - sometimes even hundreds.
It doesn't help that as the medium has become more popular - to the tune of billions of dollars in 2018 - game worlds have grown at a startling rate.
The open-world formula used to be something Rockstar experimented with, yet now it's essentially an industry standard, meaning the majority of titles are layered from top to bottom, script to environment with storytelling, rulesets and contextual elements to bring everything to life.
Look at CD Projekt RED and The Witcher, or God of War's portrayal of Norse mythology. Every last stone carving, character dress code and symbol means something, and has to line up, or eventually someone will notice if it doesn't. And they're just the obstacles of one genre.
Monitoring any number of plot threads, possibilities, in-world lore rulesets and player agency running throughout is a mighty tall order, and one scores of developers fall victim to.