Earlier quoted context omitted.
What are those technical reasons?
JavaScript engine optimization Devtools Every benchmark: https://arewefastyet.com/linux64/overview?numDays=365 Anecdotally, Firefox uses a lot more CPU, memory, and battery. Makes sense since the JS engine is so much worse. In this era the browser is just a VM for JavaScript.
Those users don't typically show up in whatever javascript-based metrics you're looking at. I don't think you'd care, either. You're literally building an echo chamber and then yelling into it that it's the best echo chamber.
Chrome is neither the "best" nor the "worst" javascript VM, nor is Firefox. Chrome is simply the most prolific. And that has nothing to do with Chrome's javascript implementation and everything to do with Google pushing hard for users and developers to switch to Chrome by putting it in front of their faces as much and often as possible. Everything from default-homepage being defaulted to Google.com, to that home page then asking users to switch to Chrome, and even "open sourcing" the engine and pushing for games and "competitors" to utilize it.
I have yet to find Firefox use more CPU, memory, or battery than Chrome. Of course I don't go around with Javascript turned on with every website either.
Given that so many websites utilize Google-based services it makes me wonder just how much of the "more CPU, more memory, and more battery" is also just "more of the same underhanded tactics from Google". Google already demonstrably does that for other products; why leave out third parties' websites from the shenanigans?