I'd be curious to see some kind of sociological studies about risk aversion amongst criminal prosecutors. Clearly an acquittal (and the associated trial) is still a huge burden to a person, so a strong motivation to only take cases you're confident you'll win makes sense to me. But especially in situations where the circumstantial evidence is so strong, I think most people in the US would consider it unjust not to pursue a trial at all.
To be completely honest, the first thing that crosses my mind is that the prosecutor might be a racist, since the story is (it seems) about an immigrant family. To be clear: I have absolutely no reason to suspect that. But something about the situation sounds off to me, and that's definitely one of the first questions that start lurking in the back of my mind.
Long story long: the optics here definitely aren't good.