The choice is not difficult to understand. What prompts more of a concern about these particular dead children (civillians, really, but since the topic focuses

The choice is not difficult to understand. What prompts more of a concern about these particular dead children (civillians, really, but since the topic focuses on children, let us stick with that) than others, is largely about the level of support from the USA government and military for the party doing the killing (talking about USA here because the magazine that published the article is The New Yorker). It is difficult to care about everything bad happening in the world, but when one's government (that one votes for and funds through their taxes) is directly standing behind it, it tends to get people (more) involved. That a lot (most? I don't know the exact proportions) of the ammunition and advanced weapons and machines that are killing those children are made and given to Israel by USA tends to get people to feel more strongly about it, too. Similarly with the funding (mentioned by a sibling comment) and the political protection.