Tibbets and his Manhattan consultants thought LeMay didn't really understand what the bomb was. Most of that generation looked at it as just a really big bomb, and not something totally new and world-changing. Hitler never "got" nuclear physics, referring to it as "Jewish science" so he didn't put any resources into Heisenberg's research.
Kind of like how I don't get Facebook, Twitter, Instagram, and have trouble using Google Drive and Google Documents to share and edit as a group.
I still only have the vaguest understanding of the physics of how nuclear weapons work. But I know they do.