We know where the money was spent, we don't know where the money actually came from. That's why it's called "dark money", its origin is hidden under layers of obfuscation and misdirection.

Now, from other sources, we know that billionaires, corporations, and literal enemy governments are donating to superPACs and other shell companies. We just can't do anything about it because the Republicans on the Supreme Court have always put party before the people, or even a sane reading of the law.