As for Trump, my view is that he relies heavily on instinct in most areas of his life, and his anti-war position seems to be based on a few instinctive positions he holds: he seems to dislike death and blood (ex: his Syria comments), he seems to dislike the destruction of buildings (perhaps because of his real estate background?), and he probably sees no personal profit (even though he has a business background, I don't believe he's involved in the military industrial complex) or national economic gain to be made from most wars the US has been involved in (he seems much more oriented toward national economic interest rather than geopolitical power games - see again his Syria comments).

As for inter-class conflict, I don't think that is too simple of an explanation. US foreign policy since World War II has been an ongoing battle of ideas, with push and pull between interventionists and non-interventionists. Neoconservatism is an ideology that sees the role of the US as the principal promoter of "freedom" and "democracy" around the world, making domestic economic conditions secondary to that goal. That ideology is opposed by many people across the political spectrum, so the influence of neocons on US foreign policy grows and shrinks with different administrations. If you read the wikipedia article on neoconservatism it says that many neoconservatives opposed Trump in 2016 "due to his criticism of interventionist foreign policies".