How Google gets you to install Chrome
You ask how does Chrome get installed on so many Windows computers. Well, to a large degree people use Google for search. When you go to the Google webpage it asks if you want to install Chrome. Only Edge has this advantage on Windows. You're never asked if you want to switch your browser to Firefox, Brave, Opera, DuckDuckGo or any other so Edge and Chrome have a big advantage.
I recommend Firefox as your primary browser with a few privacy add-ons and Edge with add-ons as a secondary browser to use at the infrequent times Firefox doesn't work on a Website. (I like DuckDuckGo and Brave for privacy as well)