It's because the powers of dumpers 
For example, i have group (almost 500+ people) full of dumpers..When the admin says buy this coin,.. hell yeah we will buy it because "profit".
Or people shift their altcoin into Bitcoin.
For example, i have group (almost 500+ people) full of dumpers..When the admin says buy this coin,.. hell yeah we will buy it because "profit".
Or people shift their altcoin into Bitcoin.
Shifting from cryptocurrency into another is the main reason why pumping Bitcoin and dumping Altcoins and causes network into heavy congested. That's why Bitcoin confirmations these days are days apart.