I'm not sure that Servo, Firefox's next generation browser engine, ever got its time to shine. They made big strides with Firefox's speed and developer tooling, but it's hard to know what was due to Servo and what was based on their previous Gecko engine. (I've heard third hand that most engineers were focused on Gecko prior to this split.)

Like their divestment of Rust (which was probably a good thing, many vocal open source advocates were concerned about Mozilla's stewardship of the project), this frees up Mozilla to work on other pieces of their ecosystem... like trying to figure out how to survive on their own, much to the chagrin of those committed to their cross platform, privacy oriented open-source browser. Hopefully the Linux Foundation can help the project find a new audience beyond Mozilla.