That meeting wasn't about business. The woman was a Russian government-connected lawyer who lobbies against the Magnitsky Act, and imo uses "adoption" as cover, as an insignificant part of Russia's response to the Act was to limit adoption. Hence the spies in the room with her. Neither side contends that it had anything to do with a business deal. It was admitted by Don Jr, explicitly, as an attempt to gain illicit information on Clinton. That is evidence of collusion, whether any charges come from it or not.