which detail best helps develop the passages theme of disillusionment and disappointment?

You can feel the disillusionment in the tone of the opening paragraph of chapter 3. Note the hard words "irritable", "clank", "unbathed"....

UNDER the rolling clouds of the prairie a moving mass of steel. An irritable clank and rattle beneath a prolonged roar. The sharp scent of oranges cutting the soggy smell of unbathed people and ancient baggage.