Who is this nitwit? It is a musical, not a documentary. Plot lines in musicals are often threadbare.
Secondly, the movie/musical skewers the principles -- the lawyer is corrupt, the public gullible, the starlets are more interested in their stage careers than the people they just bumped off. There is no mistake or ambiguity about what the motivations are or who is good and bad.
Now I didn't actually care for the movie because I'm not a big fan of musicals. But to try to demand some sort of rationality in a musical is a bit off target. Musicals are for people who like to see music and dancing. Plots? That's just a way to organize the order of music scenes.