My thesis is that all businesses are about 90% the same. They all have cash flow issues, budgeting, products and/or services, ownership (of some type), taxes and compliance issues.
Yes, depending on the industry, sector or sub-sector there are differences (about 5-8%), but CFO's as smart, energetic individuals can solve those issues by either a) learning them or b) using SME's (which they will need regardless, since one can't be a CFO and a SME on all subjects).
The last 2-5% is company culture.
So, back to the question - how important is industry knowledge to the CFO?
I'l now throw a curve, let's classify the CFO as either Strategic OR Tactical.