Basically the same thing that goes on when the market is bearish or BTC is having a tantrum. Alts always suffer during times like these, so it's pretty risky to invest in alts. But I still do, and I'm sure a lot of you do too.
Bitcoins are being pushed up to increase, and large amounts of money from altcoin is taken for inclusion in Bitcoin so lower altcoin is understandable. But I suspect that this is the way whales lead the market and deliberately make the altcoin fall off to buy on good coin cheap. I bought quite a lot of good coins during the downturn.