It's facetious (and bad 'journalism') to claim $100B vanished. It was never there to begin with: market cap isn't something you can cash in on. It's merely the result of price multiplied by supply. If you owned a significant portion of all the coins in the world, and tried to sell them all at once, you wouldn't end up with number_of_coins * price, it would (realistically) be a smaller number given the market slippage…
From the title: > $100B in Market Value When the market price of an assets drops, it loses market value.
An aggregator changed its reporting methodology. Coinmarketcap is a price aggregator, not a market. All of the markets are unaffected, it just happened that the markets that got removed from the aggregator are the ones that had the highest prices. But they're still there. You can still trade on them the same as before.