Nice !
Code:
# pacstrap /mnt base linux linux-firmware
Let's be a little bit pedantic for the record :
This command basically chroot to the first argument and install packages here.
The packages installed are the remaining parameters.
Adding "linux-firmaware" in the command simply makes the "linux-firmware" package to be installed.
There's a chance that your video driver requires some firmware and this is the reason why it fixed the problem.
So if one needs specific packages to be installed in order to have his system to boot, he can add them to this command.