As the Reddit thread quoted in that Twitter thread explains, Servo was not originally intended meant to replace Gecko. It was a research platform to explore new

As the Reddit thread quoted in that Twitter thread explains, Servo was not originally intended meant to replace Gecko. It was a research platform to explore new techniques which could be used in Gecko, and it successfully did that. Indeed, i think it was a pleasant surprise when it turned out WebRender could be ported, rather than rewritten in Gecko. It is a shame that Servo was shut down, because now there isn't a codebase focused on developing new technology; innovation has to happen in Gecko, alongside being a production system.