Zoom came along with a securre video/voice chat, sure it's American, but it was by far the world leader
Microsoft then used its monopoly in office tools to push Teams to everyone
You can't compete with a trillion dollar company offering your product as a bundle your clients already pay for, even if your product is better. Even VC money runs out eventually
Zoom has long been the most unsecure video/voice application.
Remember how they installed an open web server on people's computers which could be accessed by anyone through the web?
https://infosecwriteups.com/zoom-zero-day-4-million-webcams-...
Apple had to step in and patch it for them:
https://techcrunch.com/2019/07/10/apple-silent-update-zoom-a...
Or when they sent your chat data to Facebook?
https://www.vice.com/en/article/zoom-ios-app-sends-data-to-f...
How it was discussed on HN: https://news.ycombinator.com/item?id=22703000
Or when Zoom was leaking private information?
https://www.vice.com/en/article/zoom-leaking-email-addresses...
Or do you remember how those geniuses rolled their own crypto?
https://citizenlab.ca/research/move-fast-roll-your-own-crypt...
Or maybe you remember that Zoom has the ability to listen in in real-time on meetings held on their platform?
https://www.bbc.com/news/world-us-canada-55372493
To be fair, Microsoft already had Skype (for Business) and NetMeeting before that. It's not like they were new to that market. NetMeeting existed for more than a decade before Zoom even came into existence.
Zoom had COVID-19 play in it's favor, that's about it.
Skype for Business is the VoIP component for Teams, now. Sharepoint is the file service for Teams, too.
Basically, Teams is a front end for a bunch of old Mircosoft cloud services... plus chat. Actually more than one chat as teams channels chat is a separate tech stack from private chat. It used to be much more monlothic and then the Sharepoint people got their hooks into it.