Users mistakenly think "Google Drive = safe." However, Google Drive merely hosts files; it does not scan for cracks or malware the way an official software repository does. Malicious actors create new accounts, upload trojaned Office installers, and share the links before Google takes them down (which can take days or weeks).
For most new Office products, your account page (http://www.office.com/myaccount) provides options for getting back-up media (DVD) Microsoft Learn microsoft office 2013 preactivated google drive free