It’s true that they probably will not start their own butcher’s shop. Then again, what do Germans need? Most want affordable meat, which requires cheap labor. They want affordable houses, which requires cheap construction workers. They want affordable logistics and shipping, which requires cheap personnel.
These jobs are never going to get a top loan because that would cause inflation for everyone. And most Germans aren’t even motivated to work there even if the wages were good, because the work is hard/irregular/dirty.
Western European countries have always needed foreign workers, many of which have become part of our society such as the people from Turkey that came here decades ago. If Germany wants to continue without their foreign workers they would be immediately having around 8 million vacancies even by removing the people who don’t have a citizenship yet. Germany has one of the most aging populations in the world, there’s not a chance those vacancies will be filled without foreign workers.
Traders react to what they think is going to happen, not what is currently happening. Also they usually do not trade as emotionally, but rather based on processed information.
It becomes clear that this war is going to last and oil supplies will be further delayed, lowering economical prospects worldwide, which causes the market to react. A volatile market also creates some opportunities for profit as traders can gain both when the market value increases and decreases, depending on how they are trading (although it also increases risk). If you are skeptical, market manipulation is also a possibility as Trump administration is already being investigated for this.