The Germans' Miscalculation of Graphite's Purity in a Nuclear Reactor

The German bomb project didn't get very far because of a crucial miscalculation around the purity levels of graphite. Was that an honest mistake or was perhaps someone on the German side trying to sabotage the project and prevent the prospect of a nuclear bomb? This has been debated ever since the end of World War II. But I think the evidence is, to me at least, clear that the mistake in the purity of a let me just say what it was. It looked like a good material but it had impurities in it that soaked up neutrons. For whatever reason they missed that and therefore when they tried to use graphite it didn't work. And therefore they went to the next