Lernt – On the kever of Rambam it says שפתיו דובבות בקבר (even though he is buried under the ground and cannot “breath” – his lips are moving. I and you do not understand it, but if Chazal say so, it must be true! Also ON THE KEVER of Dovid Hamelech it says Dovid Melech Yisroel CHAI VKAYOM – kind of an oxymoron ON HIS KEVER, but we accept that (maybe you don’t but klal yisroel says ovid Melech Yisroel Chai VKayom at kiddush levana).
In your words: “Quite a mgic trick.”
Yet I tbelieve CHazal speak REALITY and not magic tricks. You are welcome to disbelieve Chazal (but they acceot that you become a kofe).