It becomes apparent speculation to suggest bitcoin or "crypto" will hit zero, as much as suggesting it will be $55,000 this year. We are seeing the birth of a technological revolution and speculation is all we have, for certainty is a fools game. Coins like Dash, Monero, Zcash, Ethereum, Bitcoin and many more are all real use case coins with well respected development teams.
It is also foolish to believe Bitcoin as the one true currency, competition is healthy in the crypto space and breeds future innovation, we need multiple platforms for choice on the open market. If we happened to be a single currency world, then it would be worthless as a commodity. So one possible way for crypto to hit zero, would be for everyone to just adopt Bitcoin.
now may be time to spread those assets to help catapult crypto as a mainstay.
Those alts with strong foundation have good fight to stay in the market, whereas those substandard projects will die easily. The coins that you mentioned have a very strong resistance to go down. And I don't think they will ever see them zero value in the next coming years. Crypto has been thru a lot so I don't think they will go back to zero without any valid reason. And at the moment, I don't see a good reason why they will go back to the bottom.