You can actually have scientists find signals in data they have no domain experience in. In a typical hedge fund the quantitative researchers will be a different group from the quantitative developers and traders. There are fuzzy lines between those depending on culture, but those three groups are broadly the front office. You really need domain experience for execution and risk management, but pure insights can be derived without necessarily needing any domain experience.

That said, quant researchers typically understand how the market works. They are just able to quickly excel without a background in it.