In this case you have multiple societies independently telling the same thing about the same society. Seems about as credible as it gets in a situation like this.

Also it’s not like killing infants was a big deal for the Greeks. There were even a bit shocked by their perceived lack of female infanticide in the Etruscan society.

I don't think it is entirely clear that the accounts are independent.

It's pretty clear.

There was no love lost between the Jews and Romans. The civilizations developed independently, and the survival of Judaism required rejection of the Roman world view in most things.

I don’t know. My reading of ancient anti-Christian polemic seems to show that Greeks and Romans familiarized themselves with Jewish sources enough to use them to bolster their arguments. One example being the story of Jesus having been fathered by a Roman soldier named Pantera.

The sack of Carthage happened 150 years before Christ was born and almost 100 years before the conquest of Judea

And about themselves to induce fear in their enemies. 'The Spartan Mirage' comes to mind.