I just read one thread about the red market "blaming" Vitalik Buterin. I find that laughable.
The real reason is people are starting to bet on BTC again and selling alts even cheap. It always go through this cycle before the alts really take off. Some also use the opportunity to collect more alts later...sell now (high), buy later (low). It can be a good way to play but very risky. I used to do it but learned I don't have the nerve to be in that game.
Play it, or HODL...both are valid ways to go. Just don't panic, bullish market is coming...BTC first then alts (may dip a little but) will follow.

This is really looking like 2017, if people recall, there were two distinct patterns that alts followed in concurrence with what was happening with Bitcoin. Early 2017, like early 2018, Bitcoin was beginning its move upwards of $1k and alts were dropping. This was attributed to people selling off alts to retake their shares of Bitcoins. But remember in spring when Bitcoin went towards $5k and ETH, Doge, LTC, and almost every alt was making new ATHs? This was crypto all in same mode.
Now we all just came off the "everything red" mode. And now it's back to "opposite of BTC" mode. Interesting yes?