Scariest startup hype you believed but learned not to be true?

The crypto currency crash of 2018 was a big one. While I bought in early I was deep into the Green. Swapped over to an alt-coin that was promising to make a Visa backed Crypto debit card for the whole world.

Took them too long, so I sold a lot then the crash happened and I sold more, never to return :)

Checked back on the project today and it seems it has not moved much since I last looked at it. No cards in other than one country! Seems like something easy to do: 'print plastic cards' that have a crypto backend, but apparently it is not.

cloud gaming is a hype, which I have spent 3 years on.