TLDR; Lack of VRAM (GPU RAM) is what makes the game crash at late game at all instances (on the giant earth map) for me.

So, I decided to play on the giant map regardless of the warning, and everything was great until the late game. I started getting random crashes, but I felt there should be a more specific reason. So, here are the crashes I experienced:

1. Crash when loading the saved late game with the giant earth.
2. Random crashes right at the beginning of the turn.

The first crash I was able to replicate. It guided me to find the "criminal." First, I opened the performance tab on the task manager and observed my components' use. At first, everything seemed normal, but even then, the game crashed. Then I paid particular attention to the VRAM usage of my GPU. It was always bordering the limit (8 GB VRAM). Every time it hovered the limit, the game would crash on the loading screen. I replicated this loading screen crash multiple times by having other applications open.

The second kind of crash also happened when the VRAM usage hovered 100% or even spiked for a 10th of a second to 100%. The game would crash. I solved this again by lowering my graphics settings on the menu screen before going into the game.

In conclusion, all my crashes have been due to VRAM usage, and I have not found any other factors to blame. Every time the game has crashed has been because of a spike in VRAM usage or because the VRAM was already high.

Side note: I will be upgrading to an RTX 4080 next Saturday and will be able to test this hypothesis.