It was beyond easy to see this one coming.
It isn't over.

Bitcoin slumped to its low for the year after seeing more than $44 billion in market value lost during January amid mounting concerns of increased regulation and the viability of the cryptocurrency.
After reaching a record high of $19,511 on Dec. 18, Bitcoin has lost more half its value as the digital token has been weighed down by expectations of more government oversight globally, fears of price manipulation, the susceptibility of exchanges to hacking and lingering concern that it’s all just an asset bubble. Facebook announced a ban on cryptocurrency ads this week.
Bitcoin declined as much as 11 percent today to $8,915, the lowest since November, in part on concern India may crack down on cryptocurrencies. That follows a spate of recent negative headlines, including a $500 million heist from a Japanese cryptocurrency exchange.

More than $300 Billion in paper wealth has vanished from the cryptocurrency market since December.
This bitcoin bubble, and cryptocurrencies bubble in general, shared all the same indicators of a mania that you could find in any financial bubble:

Irrational bullishness
Buying with marginal credit/debt (especially near the top)

And now we see the best indicator of a financial bubble of all - fraud.

A growing number of virtual currency investors are worried that the prices of Bitcoin and other digital tokens have been artificially propped up by a widely used exchange called Bitfinex, which has a checkered history of hacks and opaque business practices.
...The people behind Bitfinex issue a virtual currency called Tether. Unlike most digitals tokens, every Tether is supposed to be backed by traditional money — the United States dollar. New Tether tokens are issued when investors give them dollars. One dollar is worth one token.

Because of the credibility that comes with that tie to the dollar, Tether are often used to buy other virtual currencies like Bitcoin.

In recent months, however, many investors have been raising alarm bells about Tether. Hundreds of millions of dollars worth of new Tether were created; almost always when the prices of other virtual currencies were heading down. The Tether were used on the Bitfinex exchange to make big purchases of Bitcoin and other tokens, helping push their prices back up, according to multiple analyses of data from Bitfinex.

“This became more and more concerning, because every time the markets went down, you have seen the same thing happen,” said Joey Krug, the co-chief investment officer at Pantera Capital, which runs several virtual currency hedge funds. “It could mean that a lot of the rally over December and January might not have been real.”

My guess is that the big fraudsters have already bailed on the market, leaving the greedy dumb-money holding the bag.

That being said, cryptocurrencies aren't going to go away. They do have a place in the world, so they will retain some value. Just not anything near what we've seen.