Are there details on what visas Hyundai needed they couldn't get? L-1A/B for sending experts or management would make sense but I'm not sure there's any real issue getting those, especially not in 2023 when the plant was started.
There were here on B1/B2 Visas according to the reporting, which has a 6 month duration and rather strict requirements: https://news.ycombinator.com/item?id=45207369
If they were here in the first case of the word, I would say they were definitely in violation. If here for the second case, perhaps not but if they did not get the "B-1 in place of H-1B visa (temporary project visa): Some professionals might be eligible for a B-1 visa for temporary projects in specific scenarios. This option can be viable when an H-1B visa, typically used for specialty occupations, might be challenging to obtain." they may have still been in violation.