Not sure about your memory claim either - I don't recall high memory usage in Office ever being an issue.
Microsoft released Windows Virtual Desktop earlier this year that is basically a cloud version of Windows 10 (or 7) or Office, that’s designed to be used like Stadia.
Disclosure: I work at Microsoft but not on any of these projects
https://myignite.techcommunity.microsoft.com/sessions/81670?...
https://www.windowscentral.com/its-official-microsoft-teams-...
EDIT: Yup, the link referenced by the article (https://microsoftteams.uservoice.com/forums/555103-public/su...) says:
"We’re pleased to confirm the Teams client for Linux will be available in preview by the end of this calendar year, enabling people who use Linux client at work or in educational institutions to collaborate with others on Teams. Users will be able to install native Linux packages in .deb and .rpm formats."
As for AD, Azure's hosted services for this may well see more inroads into Linux, and I know a LOT of people/companies that would be beyond happy to use MS account management with a cleaner Linux integration.
I won't be using these things at home any time soon, but in a corporate space, MS would be a welcome and cost saving change compared to what is out there on Linux currently.