Gecko is not worse, though it used to be worse before Electrolysis landed. It's just that Mozilla Corp is mostly kept alive by Google so might as well remove the indirection and go straight to the browser that Google maintains
How much money do you reckon it costs for just the Firefox browser?
I know Mozilla waste a lot of effort on projects like Firefox OS, the Firefox mobile, politics, etc. But the actual browser it's self and it's hosting?
I just wonder if they end up dropping Manifest V2, if a patron model would work to maintain a fork properly...
Also Gecko is just a factually worse engine, that's why they didn't use it.