Why are crypto currency popular all of a sudden?

Because more and more people start to understand that we need a decentralized currency. The current world currencies like USD and EUR will sooner or later crash. Other than that, they are way more private and secure and people seem to slowly understand how important it is to have privacy, which is, mind me, a really good thing.
Everyone should at least invest a bit into Bitcoin and Monero and just keep it, one will probably not regret it.