My guess is >99% of this data refers to corporations that are legitimate businesses that are fully compliant with the law. US persons have been required for years to disclose offshore bank accounts (through FBAR reports) and other offshore financial holdings (through IRS Form 8938 on tax returns, cf FATCA). I'm sure there is a team at the IRS that is busy comparing this data set to the IRS database, and woe to anyone that has not disclosed their offshore financial interests.

But it shouldn't be a surprise that people use offshore corporate structures to manage offshore businesses. The main reason this is necessary in the US is that the US taxes corporate profits worldwide, while other countries do not (they have territorial tax systems and do not tax profits earned in other countries). So US corporations have to set up these complex structures to achieve tax rates that are comparable to other developed countries.