High lead content?
now maybe something made them sway more than they could normally take like a settling cement bedrock foundation...hard to see from here
or maybe they just weren't designed as sufficient to hold the building at that point though they did throughout the rest of the building though obviously where the steel piers snapped at the bottom would be the highest stress point
when I was a boy jap steel was considered inferior to American or German, lord knows about Chinese, Indian or Brasilian or Venezuelan