Other than the fact he has not yet placed a nuke on one of his missiles or aircraft, and they are hardly the size to be placed on a “drone.”
Seriously though, it is a big technological step to put a nuke on a missile or an aircraft as opposed to detonating one in a bunker somewhere.
I would be more worried about a nuke in a container ship in Long Beach.
Re: “They are hardly the size to be placed on a drone.”
I disagree.
25 years ago, a weapon weighing 100 pounds, that’s total weight, could deliver a 1 kiloton blast.
I agree that building these things can be very difficult.
But the basic plans are widely understood.