Hearst and his caricature Kane were essentially Populists.
We all have our Rosebuds, by the way.
Well, half of us, yes, but most of them don't ride them down snowy hills in public.
"Rosebud" in the movie was of course the sled from Kane's (long lost) childhood.
"Rosebud" was alleged to have significance to Hearst too, but referring to something (actually someone) else entirely.