Mozilla hopes its Electrolysis project will bring you back to Firefox by making the browser faster and more crash resistant
https://www.cnet.com/news/firefox-speed-boost-maybe-try-mozilla-browser-again/
They also need to do something about it being a resource hog. I have many tabs open and have see 1.6GB of RAM used, whilst I have 4GB on my XP system so it is manageable. But I think that could well be part of the reason for crashes, though I have no definitive proof.
It seems when I get to X number of tabs open it falls over, I do allow a crash report sent to Mozilla, so hopefully they get some useful information.
That however, is a moot point given XP is on the ESR build for now and not long before no support.