Changing the file ACL is tied with the file permissions bits settings.
The manpage for ACL reads as follows:
CORRESPONDENCE BETWEEN ACL ENTRIES AND FILE PERMISSION BITS
The permissions defined by ACLs are a superset of the permissions
specified by the file permission bits.
There is a correspondence between the file owner, group, and other
permissions and specific ACL entries: the owner permissions correspond
to the permissions of the ACL_USER_OBJ entry. If the ACL has an
ACL_MASK entry, the group permissions correspond to the permissions of
the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
group permissions correspond to the permissions of the ACL_GROUP_OBJ
entry. The other permissions correspond to the permissions of the
The file owner, group, and other permissions always match the
permissions of the corresponding ACL entry. Modification of the file
permission bits results in the modification of the associated ACL
entries, and modification of these ACL entries results in the
modification of the file permission bits.
When you view the ACL that you sent on file1, you can see the following output:
# owner: root
# group: root
Note the mask settings. Mask settings will be reflected in the group setting. But when you change the file settings and remove group permissions, you also change the mask settings, thus effective permissions for user myUser are ---, because they are masked.
You can read further here and change the setup depending on what exactly you want to achieve. There is no way that you could change ACL without changing permissions bits.