Servo is heavily sponsored by Igalia these days, who pay several full-time developers to work on the project.
https://servo.org/blog/2025/01/31/servo-in-2024/ shows that 26% of the PRs in 2024 were made by Igalia.
Here's a good post explaining the relationship in more detail: https://blogs.igalia.com/mrego/servo-revival-2023-2024/
It says "Things changed in 2023, when Igalia got external funding to work on Servo and get the project moving again" but doesn't name the source of the funding. It might be the NLnet Foundation - https://nlnet.nl/project/Servo/ - but I couldn't find information on the amount of that grant.