Because of the poor reporting, it's not possible to say for sure what happened, but it sounds like Hyundai/LG/subcontractors brought in hundreds of South Koreans on B visas and had them engaging in productive work. That's not what B visas are for. B visas are for meetings, sales, and maybe some light training/setup/integration. When the CEO talks about needing specialized, skilled workers, that's a strong suggestion these workers should have been on L visas.
Times reporting confirmed a few of the workers were on B visas: https://www.nytimes.com/2025/09/12/business/economy/hyundai-...
Unfortunately the same article doesn't even mention the L visa, and cites an immigration lawyer who complains about the difficulty of getting H-1B visas. But L visas are not capped like H-1Bs. In India we approved thousands of L visas specifically for skilled workers to assist with bringing plants/equipment online.
In short, the B visa is not a work visa. Most countries worldwide are quite restrictive about the conditions surrounding work visas, and people who violate the conditions of their visa shouldn't be surprised when there are consequences. Having a valid visa but violating its conditions means you are violating immigration law.
Corporate immigration departments can and do cut corners and may have thought they would save money and time by sending foreign workers on B visas (which they might have already had) or on the visa waiver program. L visa holders don't even have to get paid US-level wages, so one take on the visa type is that it is already a way for companies to undercut US labor.