Markets are cyclical, they rise and fall. But during the fall, many altcoins are already dying for ever, and when the market grows, they do not recover.
Any Altcoin that don’t have good use case and the price is just base on hype and trends onces such Altcoin dump they will never see the light of the day again, sometimes the team are actually the ones who pull out liquidity and move on in such case we can’t expect such coin to recover from a heavy fall, but if the coin have some good use they will gradually recover as their usage will speak for them.
Manipulation is everywhere, that's why I first faulted the topic of the OP, no true gem will die, it's a misrepresentation. If people temporarily earn from something, they misplace it for a gem, but that's not true, it could be their luck shinning at that time, it is all gambling in most of the listed crypto projects these days. It could be terrifying at times too for we've seen coins that pumped 50x and dropped it the same way in just a week. Should we call that a gen? Heck No!