Many years ago, a young couple in our apartment complex lost an infant. (I don’t remember all the details; I think the baby was sick for a few days before s/he died.) The funeral was on erev Yom Kippur. I, personally, had a very hard time understanding this. After davening that night, I went over to the Rav, and in tears, I asked him to explain it to me. I just didn’t understand how Hashem could take a baby.
He answered me by asking if I thought that parents would regret even one second of having their precious child with them in this world, had they known what was coming. Of course not, they treasured every second they did have. So, that still doesn’t explain why Hashem did what he did, but we can’t know that. But we can take comfort in the fact that the parents were able to treasure their baby, even for just a few days, even for just a few hours.