He didn't know who to call to figure it out
This story is really tough to believe but here is what the Huffington Post is reporting:
President Donald Trump was confused about the dollar: Was it a strong one that's good for the economy? Or a weak one?
So he made a call ― except not to any of the business leaders Trump brought into his administration or even to an old friend from his days in real estate. . Instead, he called his national security adviser, retired Lt. Gen. Mike Flynn, according to two sources familiar with Flynn's accounts of the incident.
Flynn has a long record in counterintelligence but not in macroeconomics. And he told Trump he didn't know, that it wasn't his area of expertise, that, perhaps, Trump should ask an economist instead.
Trump was not thrilled with that response ― but that may have been a function of the time of day. Trump had placed the call at 3 a.m., according to one of Flynn's retellings ― although neither the White House nor Flynn's office responded to requests for confirmation about that detail.
I think Trump is confused about a lot of things but I have a hard time believing that someone who has done so much international business doesn't know a few things about how currencies work.