If members of your Google org want to administer groups, it’s tempting to make them a “Groups Admin”.
Be careful though as this allows the person to read any message sent to any group (including historical messages), and most organisations have groups whose messages contain sensitive information (e.g. HR or payroll).
A Groups Admin can browse group messages by visiting the appropriate conversation page:
A Groups Admin has access to such pages even if they aren’t an owner/manager/member of the group.