Its hard to imagine someone not believing in the Holocaust when historians estimate today that there were 5.9 million jews killed during this genocide, but there are many people who doubt these facts. Holocaust denial is an attempt to falsify the fact the the nazis imprisoned and killed many Jews. Holocaust denial is often meant to target Jews and is often used a type of antisemitism to reduce sympathy for jewish people.
The Holocaust is one of the most well-documented events in history, the idea that it is all fake and put together by Jews to gain sympathy is simply a conspiracy motivated by hatred for a group of people. This hatred although it is found much less often is still very much around. A group known as the Neo-Nazis continue to preach antisemitism, homophobia, and racism throughout the United States and other countries. They attempt to continue the nazi political party, although this attempt is almost never successful it still shows how much is still to be done after this