This is click baity. People don't exclusively look up things they have no idea about. I'm constantly searching terms to reaffirm my understanding or to get a more precise definition of them. Oligarchy in particular doesn't have a measurable identification which of course people are going to want to dig a little into it. Hell there's a comment on here that made me dig into it since they're stretching it's definition way past it's meaning
Hell, I looked this up just now fully knowing what an oligarchy was because a) I was curious about the formal definition and b) I wanted to learn more about the history
This can be said about almost any article that claims people type a specific word into a search engine after someone says it. There were a lot of articles about people looking up jury nullification after Luigi was arrested. Or people looking up the word tariff after trump said it. It's just a quick way to find more information about the specific instance the word was used in. I didn't search the term tariff because I didn't know what it was, i searched it because I wanted to know what trump and his supporters thought it was.
Additionally, any mention of a word in a speech like that will result in an uptick in search usage – but that doesn’t let anyone quantify anything.
You’d see an uptick if a single person over baseline average looked it up from the speech, and everyone else understood it.
“X is trending in search because people don’t know it” is always a fallacy. See also: reporting on increased search for “who are the presidential candidates” a few days before the election.