Because many people see it as something coming from the right only?
All communist countries worked similiar (, besides...when people say Adolf = Fascist they tend to ignore that he was mainly a national SOCIALIST, with alot stuff in his program which would make even modern lefties smile and nod.
So there are alot of misunderstandings in that "history" and many don't know WHAT lesson to learn exactly in the first place.
1st step: find a common enemy (jewish banker, firm owners, exploiters, everybody not poor) and invent some conspiracy theories
2nd step: get your own propaganda outlets (Pravda, Neues Deutschland et al) and discredit all other news sources
3rd step: undermine the executive
4th step: begin threatening political opponents with violence
5th step: claim that the elections are rigged
6th step: start a civil war (to kill and jail opponents)
7th step: create a dynasty (or the next best party leader)