Since all cryptocurrencies are linked to Bitcoin, most of the other cryptocurrencies fall following Bitcoin as the price of Bitcoin declines, which of course is a big drop. As for why it's a good time to invest in cryptocurrencies, you can get more coins at a lower cost because all currencies are falling.
Can I know in what way all the crypto currencies are connected?
No crypto currencies are connected to any other crypto currencies,the prices are based on their demand and supply.But the altcoin prices may fall when the bitcoin prices fall because it will create negative thoughts among the investors so they will cashout their other coins when the bitcoin price falls.So it will cause other coins also fall.But it is the great time to buy coins,Buy low and sell high to make profits.