What makes you say so?
They saw potential in Rust for safety and technical guarantees, and started the Servo project. Eventually, they integrated some things into Gecko, and then concluded the Servo project.
What makes you think they don't want Gecko anymore? What makes you say they started Servo when it's a partially integrated and, more importantly, a concluded project?
Mozilla integrated parts of Servo and concluded it as a Mozilla project, passing governance to the Linux Foundation Europe. You call that letting it rot?