Eight years of obama using the military as a progressive experimental captured audience has it consequences...
And two years of Mattis doing nothing to correct those policies has further crippled readiness.
Some thoughts
The US military has often been an experimental testing ground for social change, i.e. desegregation.
The military somewhat mirrors our society and our society has deep ideological differences about our President.
The military has a hierarchy that is both authoritarian and socialistic in nature.
In our military, the Rambos are few and far between.
Thus I do not think the military would show monolithic support for Trump and his domestic policies. Yet if you would poll the military about the President's support of their institution, the result would be overwhelmingly positive.