I think that's a poor interpretation.
Yes, putting the two words "fake" and "news" together into a Google search happened prior to pizzagate. But the term "fake news" as it's understood now came about as a result of the propaganda that was spread during the election and only recently became part of our lexicon, lexicon meaning common usage.
Fake news was not part of our lexicon well before pizzagate.
Pizzagate refers to one instance of fake news, but fake news cannot be used in place of the phrase. I would say the term may have been pushed in place of "propaganda" since media outlets wanted to distance themselves from the tactics, but pizzagate cannot be used to refer to any fake news in general.
Had there been no pizzagate we would still be discussing fake news, as it is only one of a multitude of examples.