Those who have studied the fascist rise to power, see among others a common element of a populist movement that grew large and was ultimately mobilized in great number to force the system to their hands. The Weimar republic per the Versailles treaty was only allowed to have 100.000 serving men and they were also supposed to be the country's police. Hitlers "brownshirts" grew to numbers well beyond that, hundreds of thousands, and then Hitler even had a lot of sympathizers among the army. This created the situation (or powervacuum) that while the state had nominal authority over the country, defacto effective control fell more and more with the brownshits and Hitler. By the time the 1936 ellections came around, the Brownshirts pretty much controlled the ellection process with armed millitants "organizing" the ballots.
Mussolini did a similar thing with his great march. Huge angry armed mobs are no joke.
Trump's abillety/tendency to want to be able to mobilize large numbers, regardless if it might consist in part even of armed KKK'rs or rednecks, is very concerning. Anger, hate, vitriol, instabillety, distrust and fear are all usefull to fan the flames so people would pick up their pitchforks and trump knows how to use it.