> Why would Disney have agreed to a temporary license, as opposed to a purchase of this critical IP?

It was probably a risk hedge from them.. he would have wanted a lot more for the full enchilada and they didn't know how it would perform in the future. And now his work is not hard to reproduce so it wasn't a bad call. Every political data team I have heard reporting on essentially concedes that whatever they do ends up more-or-less matching 538.. so it is hard to extract surplus value but also easy to hit that mark roughly.

I follow the NHL and there are a lot of models, they disagree in certain details but they largely agree and the "winner" at the end of any given season isn't winning by much.. even private data isn't a big boost.