Imagine being told to design Google in 2000, but in order to save money you have to reuse old software: database from Oracle, OS from IBM, and design around the code from AltaVista. That should only take a few hundred man-months, right?
The top level comment did not achieve this art, but I've seen worse.
https://www.economist.com/science-and-technology/2022/08/24/...
https://www.scientificamerican.com/article/nasas-artemis-del...
https://en.wikipedia.org/wiki/Space_Launch_System#Developmen...
The NASA Authorization Act of 2010 directed NASA to develop a new rocket called the Space Launch System. It set performance requirements for the rocket (use just two stages to lift 70 tons into low-Earth orbit, use a third stage to lift 130 tons to LEO, carry cargo and astronauts to ISS, carry deep-space crew capsule, support gradual increase in performance by "evolutionary growth" with new stages), and required that, "where practicable", NASA should maintain existing Space-Shuttle and Ares contracts, workforces, infrastructure, and technologies, and that the rocket be scheduled to launch no later than the end of 2016.
The precise requirements were written to force NASA to design a rocket that maintained lucrative Space Shuttle-era contracts.
https://spaceref.com/press-release/hatch-passage-of-nasa-rea...
Also, the requirement to upgrade existing infrastructure ensured that billions of dollars went into Bill Nelson's district in Florida. (He is now the highest-ranking official at NASA.)
The law did not establish long-term funding for the development of the rocket. As with all NASA projects, money is granted one year at a time in Congress's annual budget. In 2011, NASA announced the plan to build this rocket. In accordance with the law's requirements and intention, it re-used almost all core technologies, infrastructure, and major subcontractors of the Space Shuttle. There was actually some fuss about this at the time:
https://spacenews.com/shelby-nasa-hold-competition-sls-boost...
but the strategy of "give Congress what they want" has worked: the Planetary Society shows that Congress has consistently granted NASA more money than asked for to fund SLS.
https://www.planetary.org/articles/why-we-have-the-sls
In particular, Richard Shelby (senator from Alabama, which is home to many NASA facilities, and Chair of the Senate Appropriations Committee from 2018–2021) was a powerful political supporter of the SLS, ensuring its continued funding, and attacking anybody who even suggested it might not be necessary.
https://arstechnica.com/science/2021/02/so-long-senator-shel...
Any source?