These people with the highest accountability do not hesitate to blame lowly software engineers when it suits them.

https://www.theverge.com/2015/10/8/9481651/volkswagen-congre...

Do they? They will frequently tank a company and then golden parachute into retirement. This happens all the time.

Not really true. They have the most people beneath them that can take the fall for them. Finance shenanigans? CFO takes the fall. Missed targets? COO or CMO. Major hack? CTO. Etc.

But isn't compensation proportional to the cost of replacing someone?

I can imagine a bunch of roles that are more costly to replace than "someone with accountability".

But do they do the most for the company, though? What about those who actually invent their products in R&D, or any of that?

I've yet to come across a company that pays the highest output individuals the most. That's not how capitalism works.