What lesson could be learned from this?
If you are a altcoin investor, do not keep all your eggs in one basket, if you believe in an altcoin, make sure it's not the only one, in fact, the more coins you have in your portfolio the lesser the risk, because not all the coins will go bad or get hacked, if one out of 5 or 10 become successful, 6x to , 10x or more, you've made back your ROI and still have some gains.
Provided that all the altcoins in your portfolio are all well researched, there is no perfect research because there is no guarantee that the altcoins however good they may seem will be profitable in the long haul, its good to diversify but keep following all these altcoins and always ready to trade it to better coins, to avoid massive losses, you don't have to wait for a coin to get to the bottom before trading it.