So I couldn't figure out why the installer would just freeze for a bit and then close randomly. Even after looking at the terminal as it did its thing, it wasn't really apparent.
Turns out you have no space to update. I used dd on linux and rufus on windows, same result.
sudo mount -o remount,size=2G /run/archiso/cowspace
sudo pacman -Syu
Then running cnchi worked for me. Why is this a thing?