authentication for SSH into EC2 with new user failing

I am working with Chef on EC2 instances, and created a user data script to be passed in through the knife ec2 command, which creates a new user, copies the public key file from the default ec2-user and sets the correct ownership and permissions.

#!/bin/bash
CHEFUSER="$(date +%s | sha256sum | base64 | head -c 32)"
useradd $CHEFUSER
echo $CHEFUSER 'ALL=(ALL) NOPASSWD:ALL' | tee -a /etc/sudoers
cp -f /home/ec2-user/.ssh/authorized_keys /tmp/
chown $CHEFUSER /tmp/authorized_keys
runuser -l $CHEFUSER -c 'mkdir ~/.ssh/'
runuser -l $CHEFUSER -c 'mkdir ~/.aws/'
runuser -l $CHEFUSER -c 'chmod 700 ~/.ssh/'
runuser -l $CHEFUSER -c 'mv -f /tmp/authorized_keys ~/.ssh/'
runuser -l $CHEFUSER -c 'chmod 600 ~/.ssh/authorized_keys'

Checking ownership and permissions seems to return as expected after running the script:

# ls -l .ssh/authorized_keys
-rw-------. 1 NWYzMThiMDBmNzljOTgxZmU1NDE1ZmE0 root 396 May 29 11:28 .ssh/authorized_keys
# stat -c '%a %n' .ssh/
700 .ssh/
# stat -c '%a %n' .ssh/authorized_keys
600 .ssh/authorized_keys

If I SSH in with ec2-user and copy/paste the same commands as root (which is how the script runs according to Amazon), everything works fine and I can then SSH in with the new user.