Re: be of so much importance
Perhaps the passive structure of the original sentence was hidden because the grammatical subject did not come first.
It is further complicated by the inherent negative "nowhere else was so much importance" meaning "it was not as important anywhere else."
People in New England attached more importance to intellectual pursuits than people in the rest of Colonial America did.
Make it passive: More importance was attached to intellectual pursuits in New England than anywhere else in Colonial America.
Add that negative: Nowhere else in Colonial America was more importance attached to intellectual pursuits.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.