The reason it put CC only to the last user was because you are replacing the list with only the current Iterator Value in your change variable activity.
Can you add the below code to your change variable (CCListName) activity and let us know if that worked?
Sending the typed code as reference below
trim($CCListName) != ‘’
$CCListName + ‘;’ + $IteratorAccountPIC/Email
This forum post will give you more context on what you need.