'The Second Prince came to this forest to investigate the core of all happenings in this world. Despite being an incredibly dangerous starting point, it is also arguably the best one.'
Here, Atlas could find the crux of the issue. He could find the reason why the Third Prince suddenly changed and why he poisoned the First Prince and killed the Emperor.
Atlas wasn't aiming for the bad ending. He had no connection to this world, but that was his character. Despite being selfish in the smaller things, he couldn't stop himself from wanting to preserve the bigger picture.
He couldn't allow the Third Prince's plans to unravel. And, he couldn't allow the other Ascender to ruin the scenario.
'For me to plan a course of action, I must first find what the Second Prince failed to discover.'
Instead of returning to the capital, Atlas delved deeper into the Dark Forest. He was not the Second Prince. He did not have the same flaws as that person.