It didn't, though. While radical leftism was heavily cracked down upon liberalism was allowed, even within the political sphere. Open dissent was tolerated so long as it didn't morph into calls for overthrowing the whole system. That's actually the main difference between authoritarianism and totalitarianism.I would say a monarchy that actively cracked down on any and all possible opposition, used secret police (Okhrana) to hunt down and murder any threats to its power, resisted every chance of reform in order to retain its autocratic power over Russia, and treated 90% of its own population like slaves fits the definition of totalitarian.
What reforms? Alexander III's reaction mainly involved political repression against leftists, not backsliding on Alexander II's social reforms (which in fairness didn't go that far due to aristocratic opposition). The main problem with emancipation was that most freed serfs were still tied to lands owned by big landowners (where have I heard that one before) and Alexander didn't feel strong enough to move against them. With hindsight we can say he should have, but ultimately neither Tsar was some cackling tyrant wondering how much oppression they could do today.While serfdom was officially abolished in 1861 (the fact that it lasted this long is kind of telling), the life of the average Russian at this time was still extremely awful, and most of the reforms that sought to improve the lives of the population were undone once Alexander III came to power.
Tsarist Russia was pretty terrible, don't get me wrong. But it definitely wasn't worse than Savinkov's Russia, and we don't know if KR's Restoration would be as bad; in particular, Kyrill seems like an enlightened guy(and OTL he wanted to work with the Soviets) so it seems doubtful he'd go back on the Republic's social reforms, especially if Wrangel (also a pretty alright guy) put him in power. I can't imagine the Tsar would be more likely to enact organized genocide than Savinkov.