The casual people of this world just hate smart people. It gives casual people a rush to defy or argue against smart people... even if a smart person is giving the most logical, empathetic heads-up possible. A mix of self-sabotage, sado-machoism and a dislike of being told what to do.
It's the same principles on younger people defying their parents, even when a parent is genuinely giving a helping hand with no catch. "I barely tolerated listening to my folks boss me around- I'm not listening to YOU stiffs anymore! I'm listening to the guy who wants me to have fun!"
Strangely, it's people who liked or at least better tolerated their parents -or were better able to see though any of their genuine hypocrisy and idiocy to call them on it- that are better at seeing through Trump's BS.