Writing code doesn't have a notably higher (if at all higher, vs lower!) IQ requirement compared to some of the basic components of EE or MechE work. Programmer salaries have been driven up by the ability to write-once-sell-globally and the dramatic profit margin difference between that and, say, producing chips where there's a much higher fixed cost due to the need for more real material, tooling, etc. Many of those roles require a much higher-than-baseline-skill, but it pulls up the compensation competition for almost everyone else too. (Though even then there are a lot of unglamorous, line-of-business, internal-tools-programming work that's not paid particularly well even in a lot of parts of the US far from the big tech companies.)

>Writing code doesn't have a notably higher (if at all higher, vs lower!) IQ requirement compared to some of the basic components of EE

Average IQ of Electrical Engineers: 121

https://www.iqcareerlab.com/tools/iq-for-profession/electric...

...which is the top 10% of the population.

https://www.desperateminds.com/blog/iq-120.html

Salaries are a product of supply AND demand. Supply of good programmers and EE/MechE is low because it requires above average intelligence and a lot of education, while demand for software has been much higher than demand for EE/MechE. Now that the demand side might invert.