South Korean workers detained in Hyundai plant raid to be freed and flown home

Isn't "freed and flown home" the same thing as "deported"? These were routine professionals doing a job they took in good faith under rules and norms that have held for a century or more.

The one detail I can't seem to find anywhere was what type of visa these SK nationals used to enter the US, and if they overstayed.

This isn't exactly new territory. A lot of countries are very careful to avoid letting you in on a tourist visa if you give off the appearance of entering to work.

some had no visas, some had tourist visas, some had expired visas

Well this extra context makes what ICE did totally understandable. I would expect any country to do the same.

The crackdown is certainly being done for the wrong reasons but it does seem strange to me just how much of the US is built around the idea of a second class of citizens who don't have documentation. It seems like a significant portion of farmworkers, construction, hospitality and childcare are routinely done by people who aren't legally in the country.

I'm sure there is more of this than in Europe than I'm aware of (food delivery is one example we're recently had a lot of focus on in the UK) but it's certainly not at the point that it's routine and expected.

How does this work? Are these people somehow paying taxes regardless of their immigration status?

There's been a successive series of US federal administrations that gave them a pass, either through lack of enforcement or inventing temporary work visas that also covered people who already illegally immigrated: https://en.wikipedia.org/wiki/Temporary_protected_status Biden expanded this authority to cover ~1.2M new people

Also in states like California they let undocumented immigrants get drivers licenses. They can even get bank accounts and mortgages in some states (which is basically impossible here in Canada).