I switched to Edge after it switched to Chromium and opened Edge up to the Chrome store. Mozilla kept making Firefox worse, having used Firefox since version 3.
I imagine most people use Chrome because it's the default on Android phones (except Samsung) and it allows for easy syncing, and most people have probably used Chrome since it launched and have a "It works fine so why switch when the competitor isn't offering anything better that I need" mentality, which isn't a bad. It's the same reason most people use Google search instead of Bing, and Google office programs instead of Microsoft's on their phones even though they're both free.