Because of American Liberal Socialist Progressive Marxists, and the New York Times style Western Media Bias in favor of Stalinist Socialism.
As you and others note, many Americans had, and have, a fondness for communism. Viewed in this light, it should come as no surprise that there have been so few films about the Holomodor.
Hitler and Stalin were allies and coordinated their attack on Poland. Then Hitler betrayed Stalin and attacked the Russian communist empire. It is easy to see that why communists and their supporters would hate Hitler. Pro-communism lends support to the making of anti-Nazi films.
To be clear, I am opposed to both the German National Socialism (Nazism) and international socialism (communism). Both ideologies are mistaken and harmful. Both led to the murder of tens of million innocent people in the 1930s alone.
What I am trying to address is why one genocide gets so much attention and another so little. I think the main reason is the fondness so many have for communism.