As imagined by the videographers of Squirrel-Monkey in an "unearthed VHS" (via Laughing Squid), this is what Reddit looked like in the 1980s.

Of course, Reddit was founded in by Steve Huffman and Alexis Ohanian as 22-year-old University of Virginia graduates in 2005. So, as you've concluded, the above video is a fanciful fabrication (along the same lines as this and this). The idea of Reddit on floppy disc is pretty amusing, and the idea that there was a VHS to explain it makes the idea doubly difficult to explain to anyone born anytime recently. One related question, though. if Reddit really was around in the 80s, does that mean r/fatpeoplehate was there then, too?

Related: Afternoon Palate Cleanser: The Mission, Circa 1992