RMS addressed the business model from the very beginning: it's services and consulting. He practiced what he preached.
You might think that's got a very low ceiling. But, even though it's a bad example in many ways, OpenAI showed that the ceiling is very high. And if you're morally flexible even higher.
It has an extremely low ceiling. You literally cannot make consumer-targeted software if you want to survive while writing open-source code. Services and consulting is strictly B2B, and services and consulting for open-source software is capable of supporting a population of like 1% of existing software developers. Advocating for this dogmatic ideal that would cull the field by 99% is ridiculous.
I don't know how you came to OpenAI as an example given that they famously succeeded while going closed-source with the release of ChatGPT.
RMS promotes GPL, not MIT licensed software.
When a bigger entity (e.g. AWS) decides to undercut the original creator/vendor (e.g. redis,elastic search), MIT code des not help.