This sentence, which hovers between the narrator's and Charles' voice, is meant to contrast Charles' "competence" with the empty eloquence of Holroyd and Don Jose, which in each case is composed, significantly, of general moral principles. (We will hear more from Don Jose later.) It is these moral principles which receive the epithet "illusions." Between the lines, this paragraph describes Charles' descent into bribery and corruption in Costaguana; the implication is that Charles is "competent" to do so because he is not restrained by "illusory" moral principles in pursuit of his ambition.
In the larger sense, the irony of referring to Charles Gould, the fanatically
idealistic apostle of material progress, as a man with no illusions, is readily