While we don’t know the substance of what was discussed, Musk’s presence is a concerning preview of Trump’s often reckless approach to diplomacy — as well as his disregard for the line between private interests and public policy. There are a lot of reasons why Musk should be the last person hopping on that call.

The world's richest person, Elon Musk, will take a government cost-cutting role when Donald Trump takes over as president in January.