It's because the word has entirely different meaning now than it did back then. The vast majority of people would struggle to name even one literal nazi that's still alive today. Instead we incorrectly use that term to describe people we don't like such as Trump and Elon.
The meaning is exactly the same. The problem is that people are not aware of what the political motivations were for the Nazis. The Nazis were known for their blatant anti-semitism, but you need to look at the bigger picture about why there are comparisons between the Nazis, Trump and Elon. Most of the comparisons are quite accurate and the term "Nazi" is more than just a dirty word.
Mildly to your point, people use the word "Nazi" when they should actually be using the terms fascist or nationalist.
What's funny, is some members of the GOP are labeling themselves as nationalists when they have no idea what it actually means. (Trump and one of the Karen's have notably done that.)