There are a number of factors in Vladimir Nabokov's own life that are likely to have heavily influenced his feelings on authoritarianism, democracy, and government in general.
One likely major influence is his father, Vladimir Dmitrievich Nabokov. Vladimir Dmitrievich Nabokov spent much of his life as a political radical—he was heavily involved in progressive advocacy and the defense of a free press. His work forced the family to flee Russia and move to Berlin, and he was ultimately murdered in an assassination attempt on another political figure in the movement.
Later in his life, Vladimir Nabokov—the writer in question, not his very similarly-named radical activist father—married Vera Slonim, a Jewish woman, in Berlin. As anti-Semitism grew more and more acute under Germany's increasingly authoritarian government, it became clear to the couple that Berlin was no longer safe, and they were forced to flee a second time.
Nabokov's feelings on authoritarianism may also have been influenced by his experience with censorship and the restriction of information. As it was a deeply controversial work, he had an incredibly difficult time getting Lolita published after its completion. Despite the book's message, which is actually a vehement repudiation of what happens therein, it was widely interpreted as a gratuitous and lascivious work of pornography. This may have been especially infuriating to Nabokov in light of his father's commitment to free press and the open exchange of ideas.
These are just a few of the biggest examples—the International Vladimir Nabokov Society has a great in-depth timeline of major events in his life, and you may find further evidence there to support your argument.