1. Extensions - almost anyone have some kind of extension installed, and Chrome absolutely wins in that category. that prevents people from switching over to Firefox. Personally I know people that switched to Firefox only after I showed them the extensions they us or an alternative exists on Firefox.
2. Advertisement - Google have a lot more advertising resources than Mozilla. For example, every new Android phone with Google Play Services ships with Google products already installed including Chrome (sometimes as the only browser). It's not unfounded to think that most people will use the same browser they're using in their smartphone.
The fact that I can run extensions on Firefox for Android is a huge enough win that it's my default system browser.
Another issue is he press. The press is usually very Firefox-positive and always covers it. They might turn on Firefox if it started blocking ads.
I have a bunch of extensions installed on Firefox and don’t use Chrome. What are the Chrome-only extensions I’m missing that means Chrome “absolutely wins”?
One specific circumstance which impacts me is the Capital One virtual credit card extension (https://www.capitalone.com/applications/eno/virtualnumbers ) which if one clicks on "Get It Now", from a copy of Firefox, one ends up on the webstore: https://chrome.google.com/webstore/detail/eno%C2%AE-from-cap...
Even consulting the page source (view-source:https://www.capitalone.com/applications/eno/virtualnumbers/) shows some mentions of Firefox but certainly no mozilla.org URL or .xpi that would imply they're serious about that claim.
No per site process isolation, Firefox on X11/Linux is baaaad, and that's just the beginning.
X11 is an old display protocol predating modern concepts of application sandboxing. It gives gives windows lots of control, like allowing them to move the mouse, enter keystrokes, etc. Basically, anyone who has an X11 handle has the same level of access as the user. In Firefox, the process that's supposed to be sanboxed (the content process) has precisely such a handle.
So you pretty much have to have Chromium as a backup if you ever need to research non-Anglo content.
I can see people moving to Chromium because of this and other similar problems with extensions being broken (like the tridactyl thing).
Since you mentioned Tridactyl you might be interested to know that I wrote my own command to inject Google Translate on demand [3].
The extensions you mentioned were removed because they execute remote code. Mozilla are trying to tighten these restrictions [4]. I think Chrome is moving in a similar direction. I don't think that will affect the user script work-around as they execute in the page context, but I could be wrong.
[1]: https://addons.mozilla.org/en-US/firefox/addon/violentmonkey...
[2]: https://greasyfork.org/en/scripts/9285-translate-google-tool...
[3]: https://github.com/tridactyl/tridactyl/blob/c776f722944714ee...
[4]: https://blog.mozilla.org/addons/2019/12/12/test-the-new-csp-...
[1]: https://github.com/violentmonkey/violentmonkey/graphs/contri...
[2]: https://github.com/greasemonkey/greasemonkey/graphs/contribu...