Were chickens present in the cultures 2000 years ago when the taboos developed? Honest question.

Yes, they were. Chickens are one of the oldest domesticated species by humans.

Because it's not as dangerous as eating raw pork. Relatively speaking, raw pork is much more dangerous.

The data doesn’t back this up though. More people get sick from chicken.

We are not talking about quantity, we are talking about severity. Plus, you can't use modern data for this because modern stock raising methods mitigate a lot of the dangers from pork.

The parasites from undercooked pork can be very dangerous.

Why wouldn’t we use modern data? We’re not living in the past.

Are you talking about trichinosis? I can see that being more problematic than salmonella in historical contexts, but again, it’s highly treatable today and rarely fatal if it isn’t treated.

Am I missing some other kind of infection?

Edit: Now I see it, you were referring to the past in the parent comment. I’ve confused this thread for another - sorry about that!