This will help you understand here: https://themerkle.com/what-is-the-flippening/
However, I’m going to quote from Hacked.com 23/5/2017:
The total value of the coin market is now at $80 billion, as the last two days added almost $10 billion to the capitalization. Bitcoin almost doubled since breaking out to new highs a month ago, but its market share is now only 46%, proving just how strong the recent weeks have been to cryptocurrencies.
Now I’m going to show you a screenshot from Cryptocurrency Market Capitalization 24/3/2017:
If you look at the top of that picture you’ll see bitcoin had (2 months ago) 68.2% of the market cap of the total market of $23 Billion.
The simple thing here is that the market is leveling out and this could not have happened without a real player (Ethereum) coming to the market.
You can follow it yourself HERE : https://coinmarketcap.com/
