Huh? Hiroshima was a nuke. Nuclear explosions don't need oxidizers, are not limited by the O2 in the air and combustibles on the ground, etc. Their secondary effects (fire, burning, etc.) might be, but the original explosion doesn't need anything but room to grow.
The release of energy by a nuke occurs entirely within the warhead -- not counting comparitively minor secondary effects. What we think of as the explosion is actually the superhot small ball of energy reaching equalibrium with its environment, which requires a LOT of expansion.
In contrast, explosives that burn (i.e., don't have their own oxidizer) are actual ongoing reactions -- think SUPER fast burning, so available O2 can become a limiting factor. FAEs address that problem by mixing their "fuel" (explosive) with the air before detonation, ensuring plenty of O2. Another poster explained the nature of the explosive used consume less O2, but I don't know that much about that.
In any case, NO conventional non-nuke weapon is significant compared to any (non-tactical) nuke...
Nukes wouldn't work as well unless you used excessively powerful devices.
BTW, anyone hear the urban legend that some of the scientists who set off the first nuke thought it would start a chain reaction in the O2 in the atmosphere and basically glass the planet? Wonder if it’s true. If it is, can you believe they set it off anyway?