Because in March until May, the crypto market have many change, special after big profit from altcoin Ripple, some people buying it and holding just one month, they have profit x15 from @400 sat per coin to @7500 sat per coin. Then, the market have hot trend investing to altcoin cheap price, and making many investor from anywhere are interested crypto market. And the result after all happens is all crypto on market increasing
In my opinion, top 5 altcoin after Bitcoin always LTC, ETH, ZEC, DASH and XMR, because they have a huge communitity and the age of them long than other altcoin top 5 on market in current.