Amazing to see how lately some altcoins are green and high when almost everything is red.
Ofcourse sometimes really EVERYTHING goes down when BTC goes down, but i think it shows that people want to make use of the current cheap Bitcoin prices, so they sell altcoins that are on a high price now to have maximum profit and buy BTC because that's so cheap now.
It's the day-traders that cause this high correlation.
Yes, now this happens from time to time, but it was a rule almost 1 month ago (all alt-coins going their way, totally independent of bitcoin). But, now, most days, if you check all graphs of the main 200 coins, 95% fall when bitcoin fall, and go up when bitcoins go up. It could be concebible for the best 10 alt-coins (because maybe big groups are doing some kind of hedging), but if you take a look at the first 50 coins, most are related with the movements of bitcoin. And it was not like this until 1 month ago or so.
For me there is nothing surprising in this. Bitcoin is the basis of the cryptocurrencies and its high liquidity was obvious and predicted by many experts. All other coins depend on his course.
Bitcoin has been the basis for most alt-coins but most alt-coins movements were totally independent of bitcoin until 1 month ago or so. One could go up 34% while bitcoin was +4%, and other +21%, other -32%, and so on. Now, most are up when bitcoin is up, and downs when btc is down. It did not happen some months ago.