Well now, "did history really happen" is a more complex question than it might first appear because the devil is, as we all know, in the details. I wrote about the topic of how we know history really happened years ago in this post, it's still relevant today and very much applicable to the case of the Holodomor.

Holodomor and Vladimir I
Vladimir I and the Holodomor have a few things in common. Beside the connection to Kiev. Most notably, there are several conflicting accounts about what actually happened, many of which were created by people with a vested interest in promoting their narrative. In the case of Vladimir I and the christianization of the Kievan Rus the interest was in glorifying Vladimir, in the case of the Holodomor the conflict was between opposing political systems.

So, we know that at the time there were already conflicting accounts. Some claimed millions were starving to death, others that it was merely a bad harvest and a bit of malnutrition. Some westerners with no outward motive of supporting the Communist Regime were even invited to visit Ukraine and reported that nothing was happening. They were of course there by invitation of the regime and shown only a carefully orchestrated view of the Ukraine. At the same time, mentioning the famine in the USSR meant a 5 year stint in a gulag so you could learn the true meaning of hunger. If on the other hand you said that the famine existed and that the government was to blame you never had to go hungry for the rest of your life. Because your life ended very quickly.

Now, hardcore tankies will say that this is just western propaganda but the historical method would beg to differ. There are a multitude of eyes witness accounts of the famine as well as a strong written record documenting it. Against this, there is one narrative that says it didn't happen which has a vested interest in presenting that narrative. We can apply the same method here as we did with the Primary Chronicles. Yes, that narrative exists and it's still useful but we need to keep the bias in mind. In fact, the Soviet response of taking the Goscomstat (Государственный комитет по статистик) data and locking it away for 50 years as well as executing three successive heads of the same agency (until the fourth one decided that maybe the truth was not the best way forward after all) is pretty telling in itself. The data was so bad that there wasn't even a way to falsify it.

Other pretty notable things we can access thanks to post-USSR declassification include propaganda posters denouncing cannibalism (which is a totally normal thing to put out if cannibalism isn't rampant, right?) and court records showing over 2500 people were convicted and executed for cannibalism over a 2 year period.

The Holodomor and the Historical method
Applying the same method as we do for any other historical event yields the same result for all historians. It happened. Millions starved to death. It was undeniably the result of Soviet political policy. However, there is one question there is no strong concensus about. The genocide question. Was it the explicit intention of the Soviet government to cause a famine in the Ukraine or did it happen as a result of really bad government policy and ignorance? And here, just like in the case of dear old Vlad, we may never truly know. It could have been merely bad policy, incompetence and ignorance but it could also have been an intentional effort to cow the farmers of the Ukraine. The distinction is largely a question of intent and just like with Vladimir I we may never truly know what the intentions of Stalin, Lazar, Molotov, Kaganovich and the others involved were.

TL;DR - The famine in the Ukraine absolutely happened, the only question is how many people died and whether or not it should legally be classified as genocide.

If you're interested in reading more I recommend:
Anne Applebaum - Red Famine - Stalin's war on the Ukraine
Century of Genocide: Critical Essays and Eyewitness Accounts - Totten et al.
Excess Mortality in the Soviet Union: A Reconsideration of the Demographic Consequences of Forced Industrialization, 1929–1949 - Rosefielde
Stalin's apologist: Walter Duranty, The New York Times' Man in Moscow - Taylor