That's because lore from Fallout 1 shows that Fallout's universe never used realistic nukes, and always used nukes with little explosive power, but far greater radiation output. Lore has directly shown that part of the universe is unreal, whereas lore has shown other parts, such as people being able to fix boats and sail them, is something that actually happen.When we use reality as argument, because the ruins and effects of nuclear detonations in Fallout 4 are not very believable, it is ignored.
A very slippery slope. And not a good argument in my opinion.
You hardly really SEE a nuclear detonation in Fallout 1 and 2, up to the very end of the game, while they are one of the most common things in Bethesdas take on Fallout. Which is the point. They become another goody. Another tool for the player. Another simple ride in the theme park that is now Fallout.
You have nuclear cars exploding left and right, you have the player runing around with a portable nuclear catapult shooting little bombs, Liberty Prime is throwing little nuclear grenades, Megaton is killed by a nuclear device that is smaller than most conventional explosions. And now you have Super Mutants exploding in little mushroom clouds. I wonder why no one bothered to do the same with the Power Armor.
Do we really know what the size of Fallouts nuclear weapons are exactly? I would say neither F1 nor F2 really give us enough hard informations, it is for the most part Fallout 3 and 4 that give you this impression that anything nuclear isn't much bigger than a bomb. But even if you accept the fact that they are downsized and not comparable with nuclear weapons from the real world, it still doesn't make much sense what you see in F3 and F4. Using some concept art or trailers from F1 and F2 to justify it is in my opinion grasping for straws and not really the point anyway.
No one here expects hiroshima or super duper accurate absolute 100% realism. But considering the sheer number of nuclear devices and explosions in the game ... it completely trivialises it.Its not an all or nothing situation, and the fact that you tried to reduce it to such really shows how desperate you are.