The author's mastodon account has a couple of examples of the creation process if you go back through their post history a bit. It seems they used Blender for everything (as far as I can tell).

They also posted a lot about the entire process at blenderartists.org, and have apparently been working on this since February 2022!

https://blenderartists.org/t/tenochtitlan-wip/1360197

They're over here [0], if you want to try and ask some questions!

[0] https://mastodon.gamedev.place/@thomas_kole/1109968242633959...