Q:

How can we justify such disparity in closing/downvoting questions?

Someone asked a question on EE.SE:
Does this strategy for crossing electrified water work?
The asker said it was based on this previous EE.SE question:
Does a dangling wire really electrocute me if I'm standing in water?
You'll notice that one of those has a score of -4, and is closed. The other has a score of 48, and is protected. 
At first I thought the positively received question must have been from 5+ years ago (back when the community was more accepting), but it's only 2 days older than the question based on it!

Does one question very much deserve to be praised, while the other
shunned?  
Are either "on-topic"?  
How can we explain the disparity in voting and closing?

A:

The original question (the second one in your list) hit the HNQ and tickled the funnybone of a large number of outside visitors, who proceeded to upvote it and the answers. That does NOT mean that it is a good question for the site.
It could be argued that the original question should have been asked on Skeptics.SE, but because of its technical nature, it ended up here. The second question asked for pure speculation, which is off-topic pretty much anywhere, with the possible exception of Worldbuilding.SE.

A:

As Dave mentioned, the first question hit the HNQ and received a lot of off-site attention. There's definitely a very real safety aspect about it, and it's not asking a ridiculous scenario. The answers provide real-world examples of possible hazards, anecdotes to back up justifications, and explanations based on fact. 
The second question is a purely hypothetical question. From the help section Don't Ask: 

To prevent your question from being flagged and possibly removed,
  avoid asking subjective questions where … you are asking an
  open-ended, hypothetical question: “What if ______ happened?”

