Complex sentence: The notion of fidelity did thus not refer to an ideal or an athic, but to Hitler personally and his delegates, in live with the "Führerprinzip" of Nazi ideology; "fidelity" was to be understood as blind and absolute obediance.
Split into simpler sentences: The notion of fidelity did thus not refer to an ideal or an athic, but to Hitler personally. In Nazi ideology, "fidelity" was to be understood as blind and absolute obediance.