Yes, it was a conspiracy by Adolf Hitler and the Nazis to round up and murder Jews, Gypsies, Homosexuals, and those deemed mentally ill, anti-social (including many prostitutes), and other undesirables. Historical evidence clearly demonstrates this in spite of the many people who try to deny that there was no such conspiracy.
I don't see how we can fundamentally say that the holocaust happened, when there is no evidence. At Auschwitz there are no gas chambers. The room, in which they claim to be a gas chamber manufactured by the russians after the war. The central wall was knocked down to create one big room. There is no system to regulate air, or and temperature. Zyklon B needed to be at a certain temprature to create the chemical reaction and release hydrogen cyanide, unlike Zyklon A which reacted with water. There are no prussian blue marks on the walls, and the only Zyklon B was only used for delousing clothes. History is written by the victors.
Why would anyone even think this. Of course not, this question is stupider than any thing I have ever heard. They have evidence of the nazi's, their cause, and it is obvious that the holocaust was real. If it was a conspiracy to hide something, I highly doubt they would kill and start a world war to hide whatever it was they would have hidden.
The holocaust happened and it happened to the extent history claims. It was not some conspiracy to get us to go to war or fight Germany. All of the evidence points to it happening and the deniers who say it did not happen to the extent the evidence says are willfully ignorant and blind.
There historical evidence is deep and straightforward. The Holocaust was a horrific and real event. It would not be possible to conduct such an extensive conspiracy. It is true that sometimes certain groups of people milk the Holocaust for all that it is worth in terms of eliciting sympathy decades later, but it was a tragic and real occurrence.
I'm assuming the question is asking whether or not the Holocaust really happened or it was fabricated by historians. The answer to that would be an unequivocal "no." The Holocaust was very real and affected many families throughout Europe and the world. Millions of people were dragged from their homes and killed. There are records of this happening.