"Note: In the installation image, systemd-networkd, systemd-resolved, iwd and ModemManager are preconfigured and enabled by default. That will not be the case for the installed system."
https://wiki.archlinux.org/title/Installation_guide#Connect_to_the_internet
So you probably didn't set anything up. Arch-chroot in to fix, or use a cable or phone tether to fix it from the new install.
Idk how to set up it with systemd suite, but for network manager it's pretty much
# pacman -S networkmanager
# systemctl enable --now NetworkManager.service
Quick, someone make a yt video that explains even less with more confusion and a word from our sponsors!