If you take a look at Trump's last speech, people supposedly enthusiastic for Trump were checking phones or just wandering off.
Trump's not actually DOING anything, and his base knows it.
They support him over the Republicans in Congress for a very simple reason, the congressional Republicans are worse. And they know this. Congress has deliberately screwed over the middle of the country repeatedly - but they don't trust Democrats to change this because Democrats don't even bother to come to their districts and campaign any more.
Campaign in all 50 states is just lip service as far as I can tell. As soon as Hillary tried to expand her campaign, she was attacked from every side telling her she was crazy.
Though I never could understand running someone with that many decades of made up dirt on them anyhow.