The story doesn't mention that the logo came from a forum on a site called Armchair General. The logo was the start of a joke thread that announced the image as the new Democrat Party logo. Chances are that Google saw this site as being somewhat reputable/popular, found the image, used the phrasing as a signal, and noticed the post time. Those could have been enough points to automatically get the logo updated. At least that's my assumption so far, anyways.
Likely the image was changed on Wikipedia and by pure chance Google was spidering the page during the time the altered image was active. If so, going through the image and page history on Wikipedia should point to when it happened.
knowledge panel has been so consistently bad that it's a wonder people don't complain more. Half the time all I get is a random irrelevant excerpt from some website with all the formatting screwed up. If you're multilingual it'll show up as a random mix of two or three languages too.