This is pretty standard in all industries. Most people who work at a bank aren't financial experts. Most people who work at a hospital aren't medical experts.
Thats because most roles aren't the core of the business. Most are supporting the core. You don't need to be a flight engineer to build the system that tracks parts during manufacturing. You don't need to know how swaps work to build an order management system for traders. You don't need to know how to do surgery to build a scheduling system for the surgeons.
What do you work on, and how much prior domain experience did you have? (And if you did have some, was it necessary?)
I currently work for an agtech company, the domain-specific stuff is just context for the generic numbers and equations, or a reason to choose one over the other, to the extent that I need it it suffices to have a colleague who's a domain (but not software) expert.
You might say that's the other extreme, aerospace is different, but I don't really see that it is. I don't think anybody's claiming SpaceX doesn't have or need aerospace engineers, but once they've, idk, specified a formula for a parabola representing a flight path say (yes, I don't know what I'm talking about!) then the domain doesn't (needn't) matter to the software engineer implementing it.
Flight paths and what not are crafted by GNC engineers who hand them over to software engineers to implement. Really the only domain expertise needed in software is for space-grade fault tolerance, which is a couple people per vehicle.
Iv'e worked with aerospace sims, grid-level protection products, financial products for banks and safety-certified industrial control software (even nuclear in some cases) that will result in great property damage and even death upon failure.
Basically nobody in any of those places had any domain knowledge outside that which was learnt during the act of developing and, in some rare cases, some "familiarization" courses during a day or so.
Thats because most roles aren't the core of the business. Most are supporting the core. You don't need to be a flight engineer to build the system that tracks parts during manufacturing. You don't need to know how swaps work to build an order management system for traders. You don't need to know how to do surgery to build a scheduling system for the surgeons.