Why were so few materials salvaged from Ise and Hyuga, compared to their size?

benzene7 said:

Why were so few materials salvaged from Ise and Hyuga, compared to their size?

A good question, especially when there's such a vast difference between sister-ships Hyuuga and Ise.

I know that the whole "Aviation Battleship" thing was because Hyuuga suffered a turret detonation, and they decided to just put a concrete airstrip on her stern rather than replace the missing turret. (Those turrets were so massive that after making an airplane hangar, they had to lay down a foot or so of concrete just to keep the ship's balance.)

I'm guessing the problem is that, after a ton of makeshift repairs to keep the ships afloat, some of them just had steel that wasn't of high enough quality to be worth trying to recover, anymore. (The US, in fact, was more inclined to just sink its leftover ships as target practice specifically because recycled steel was so much lower in quality than the stuff it could pump out in greater quantities than it could put to use.) As such, it could be that chart's a measure of mass divided by quantity of abuse it suffered.