If you read the comments here you'll find the author saying "I don't want to promote a 2nd year business student's work as an original pitch deck so I can look more closely into the provenance of problem slides if you could name these and I'll either redact them or adjust the title accordingly. Thanks for bringing this up :)"
Don't think it's quite as dramatic as you imply here, and I don't think anyone is deliberately fabricating slide decks in order to trick you.
The site claims these are original pitch decks from famous companies. Exciting!
So, I look at a a couple, but quickly get the feeling that these may not be genuine, that this site might be theonion of pitch decks, or something. I go to HN comments to see what others think.
I was disappointed to find that the author of the site apparently doesn't really know if these are real or not. I'd like to see more than a passive aggressive "oh gee thanks this was a fun project 2nd year business student blah blah I'll look into it", when the site clearly claims to show me “Facebook's original pitch deck” as the FIRST one which is very obviously not genuine.