Occam's Razor: offshore wind requires a lot of rare earths for their magnets and whatnot. US military-industrial complex needs the little remaining global supply not under China's export controls.
This could very well be the excuse they're using. The reality is almost certainly more petty than that given the great one's irrational hate of wind power.
Any electricity produced by turning generators will require rare earths. This includes, every current non-trivial electricity source with the exception of solar. Gas, oil, coal and nuclear all work by heating steam and running it through a turbine that turns a generator that makes electricity. For hydro, the falling water turns the turbine/generator.
So any source of electricity that may replace these wind turbines (other than solar) will require about the same amount of rare-earths. And lets face it, Trump is doing his best to hamstring solar as well. He has cancelled all solar subsidies and has hit solar with major tariffs.
I think Occams Razor would lead to a very different conclusion.
AFAIK, modern wind turbines use types of induction motors because it allows them to adjust the rotation speed by applying a counter-rotating stator field (which is a very neat trick) - older turbines had to rotate at a fixed divisor of 3600 rpm (grid frequency).
