from dictionary.com:
Demagoguery is an appeal to people that plays on their emotions and prejudices rather than on their rational side. Demagoguery is a manipulative approach — often associated with dictators and sleazy politicians — that appeals to the worst nature of people.
Explain what is irrational about Trump’s campaign issues.
Today we would say "clever marketing" and "creating a powerful image" -- Trump is a master at that.
Now as far as issues are concerned, I think he's overstated the ability to keep American companies competitive across the board. Yes, in the near term, he can take steps to keep jobs and money in the country, but international product/service quality has improved to the point that you can't keep all industries through protectionist policies.
The Trump ties, for example, are made in Asia and if you did not source from low cost suppliers in Asia (and elsewhere) then retail stores would dry up because you could not afford to hire the people who stock the shelves and work the cash registers.
So this is an example of where Trump is overstating the case, I think. OK, so why do I think Trump is doing this? Because he needs blue collar votes to win -- and winning will save the country. We can't afford to let Hillary win: she would destroy the Republic.