The reason why Cryptos have seen a serious correction over the last weeks.

Reason 1:
Obviously fear uncertainty and doubt, caused by the whole 1 of August non-event for Bitcoin,for the one that have been living under a rock last 2months:
with the rise in demand of bitcoin (Japan etc.),it became apparent that the Bitcoin-blockchain was not initially designed for high volumes.This developed into a dispute between the stakeholders on how to solve the issue.Which has led to lenghty discussions that came out in the media.
I say non-event,as this will be solved and the outcome will be good for all parties involved I am convinced, as none of the stakeholders want to throw this baby away with its bath-water. Especcially with competitors lurking to take over the market.
Reason 2 : speaking of the competition; all ICO's on the Ethereum blockchain that have been issued over the last few weeks,wether legitimate or not,have started to liquidate their raised capital from Ether to fiat which makes sense ,as assets needs to been fullfilled in fiat currency unfortunately.So experts,office-spaces,machines and what not,still need to be paid with 'real world' money .
Thus causing a sell off,of sums of Ether and again causing fear uncertainty and doubt etc.
Reason 3: Other market forces as ; like the fed doing a 180 on interest rates,causing a lot of institutional money to be pulled back and returned into the debt based stocks and derivatives market.
Reason 4 :aand this is purely speculative and reflect merely an insight I had throught comparing marketcap numbers over the last months.
The velocity of change in marketcap makes me suspicious there are indeed enormous players testing the waters,say (central) banks and consorts..
Looking at the huge brief spikes we have seen on the daily charts,right before this much needed correction I can think of nothing else really..

As soon as the debt based markets finally come to a grinding halt or an explosion,I think we shall see another exponential boom in the crypto-shpere once again.