Try reading Mein Kampf some time. There’s an entire chapter dedicated to a “conspiracy theory” about British propaganda. The only “problem” is that Hitler is spot on w/r/t the lies the Brits (and to a lesser extent, the Americans) told about Belgium. But the following chapters of Mein Kampf assume an equally large conspiracy by Jewish people, which isn’t true. But you can see where the weight of the first assertion (the British gov’t were actively using bullshit propaganda to demonize Germany) carried its legitimacy to the second assertion (Jews secretly control the world).
As soon as governments begin to lie and distort the truth, conspiracy theories will bloom like mushrooms after the rain.