No one expected “Chicago” to become this big a hit. “But the movie’s domestic box office is now double that of ‘Moulin Rouge,’ the only other movie musical to fly in years, and, unlike that predecessor, ‘Chicago’ didn’t have to throw in David Bowie and Beck to entice the musical-phobic youthful demographic thought to spurn show tunes by John Kander and Fred Ebb. Young audiences have turned up anyway. Everyone has. The film has touched a nerve this year as no previous incarnation of Watkins’s play (there were two previous film versions) ever did.” Why? Even though the musical traces its roots back to 1926, its themes are timeless.