zdnet[.]com/article/heres-why-you-might-see-office-pwas-auto-installing-on-windows-10/
The problem has likely been fixed, but if you have the new Edge browser installed you should probably check to see if this happened to you earlier this month. Due to a bug, the new Edge browser was *sometimes* installing the web app versions of Microsoft Office apps, and while that bug's been fixed, those apps remain installed until you uninstall them, if of course you want to uninstall them.