In theory you can use memory to precompute almost everything as an acceleration technique. For example, imagine you're asked to do integer division (in some range, let's say 0 to 100) without hardware acceleration. Now you could precompute all 0 to 100 by 0 to 100 division options (10000 total), and store the result of all of them in memory. The next time you're asked to divide these numbers, you can look up the answer in memory instead of having to do the computation.
This is always a tradeoff using many heuristics and guesses for what's worth precomputing and what's a waste. Then there are also systems used (by for example Chrome) where the app looks at available RAM and stores more precomputations if the PC has more RAM.
But no, this is not why Firefox works fine. There was a rewrite of Firefox's rendering engine a few years ago, search for "Firefox Quantum" if you want to know more. They shifted to heavy GPU acceleration, which brought it on par with if not above Chrome's rendering performance.
The big issue with Firefox is that the Android app still feels unpolished, and people like to use one browser across devices for password/bookmark sync etc. They simply don't have the manpower to compete with Android Chrome, which has the entirety of Google behind it. It's basically their flagship product combining Search Engine, Android OS, Chromium and Material Design all at once.
I can't believe they still remember this existed. I have watched this show almost 10 times during highschool and was always sad about how the story kinda went nowhere in the sequel movie. It's a world that will probably never be expanded upon, I would've watched any additional content they made.