No nobody had to assumed that this was going to happen. I doubt that the price would have dropped for like 50% if there was no bad news from China.
A 50% drop is very reasonable, compared to how much BTC has risen lately. It's painful for the people who bought high, but it provides an opportunity for more people to buy, which should ultimately take the price higher.
Nobody could have predicted the bad news and panic sells. The bad news was really the only thing that could cause what it did.
Anyone with stock market trading experience could have predicted the drop. Just not the exact moment. I didn't expect it myself, but that's because I have money invested, and I want the price to stay above $1000. But while Bitcoin may be new, the price action is nothing that hasn't been going on since the stock market of the early 1900's.