>>58840615Explosions are a force, not just fire. Plus making it Fire would have nerfed it in Gens 1-4, arguably at least.
If Explosion was Fire back then, you’d see a lot more Pokemon tank Explosion since there are more types that resist Fire.
Since back then, Explosion had effectively 500 BP, you’d always KO anything neutral unless it was like the single bulkiest physical wall or you were using Electrode. So you’re pretty much never need to hit super effectively anyways.