re: Cate Blanchett's 2 Oscars

It's not different from a lot of winners - she got the benefit of not only a good script, but a unique character on both cases. Forrest Whittaker got the same thing in Last King of Scotland. Tom Hanks in Philadelphia.
Now credit to them for carrying those roles out. But the roles themselves helped.
The harder route is turning playing average Joe into an oscar winner.