He's not a fascist in an ideological sense but his malignant narcissism makes him an authoritarian, which makes him a characterological fascist (or close enough to one so that the technical differences don't much matter). The essence of Nazi fascism was an authoritarian cult of personality, so it was Hitler's personality that sustained the regime. The same is true for the Trump movement. What matters isn't the set of policies, which can change with the dictator's whim, but the monstrousness of the dictator's legendary authoritarian personality.