Their goal, for simplicity, is to show Mozart as a rebel controlled by noble wicked, dying in poverty for attempting to emancipate and foreshadowing the Revolution - Marxist vision totally anachronistic. It is recalled that extracts from the book were published at the time in a Communist newspaper.
Moreover, judgments about the works of authors (enamelled many chronology errors) show the weakness of their musical knowledge.
Musicology has since shown a different face of the composer, this book is hardly evidence that such a vision dated, very romanticized and tendentious.
Instead, read the works of Robbins Landon or the composer's correspondence to discover the real Mozart.