Any idea what changed, if anything? Court decisions made in the meantime simplifying things?

Hopefully the content fits in a few buckets (cartoons, fiction, non-fiction) as far as different terms for rights might go. And then from there, you can lop off anything that's past its copyright term (?). Then maybe the next step is grouping works by the agent/publisher, if any? Or maybe all the contracts with the New Yorker are signed by individuals, with the New Yorker as a publisher. I don't know.

I assume it was a matter of time - ten years of digging into contracts or chasing people/agencies down (speculative on my part)? Bear in mind, if you are unsure if you have rights to a piece then you cannot use it until you know for sure - I am sure that was part of it too.