Looking back at the 1900's, there is one sort of people who stands out. Guys with huge fame, even though they were well known as the perpetuators of shit that gets you locked up instantly in any normal society (Hint: not talking about glam-popstars).
Before the modern times we live in (yes, people lived before our times, funny but true), people were generally ruled over by kings and queens, who themselves were chosen by god. Or by family heirloom. Or by the most rad haircut in all the land (In the case of a certain empire, the complete opposite).
Regardless, monarchy went out of style after a while, as people felt it wasn't a democratic process. Countries like Russia then spearheaded the glorious victory of the people by taking the power by force and murdering the tsar. Yes.
Not all countries were as direct as Russia though, quite a few countries had democratically elected people who felt that the process that got them in the office shouldn't work both ways. Think of it as wanting a sort of lobster cage approach to democracy. Picture that for a second, i'll wait. All done? Good.
The sad story of democracy gone bad.
The most famous example of this approach to becoming a dictator is Nazi Germany, where the people of the world learned once and for all that voting in a war-scarred angry man who felt the country needed more nice things wasn't such a good idea. This same mistake was never repeated ever. 
What makes a dictatorship just that generally just means that you need to turn over a large percentage of the power to a single individual or party without possibility of taking it back. Think of it as playing pokemon with that 6th-grader who always wins and totally dupes every kid in school out of their charizards. Douche.
A valid analogue for power and influence.
Most, if not all, dictatorships goes farther than that definition though, not to be outdone by anyone else in history. (Hey, what's the purpose of seizing absolute power over a country, if you're not gonna get some gulag action going? Just sayin').
The dictators themselves are most often, if not always, the center of attention in a dictatorship.
Yep. The People of the glorious republic of North Korea were pretty distraught when their dear leader passed on. Not to be outdone by his father however, Kimmy's son is pretty much a deity in North Korea. A deity with a crack photoshop team.