Because the price fell dramatically from a release of information that wasn't from Google. Until its confirmed by Google it's just speculative which NASDAQ doesn't want.
Because the market is "stabilizing" on possibly inaccurate information that was not meant for release. It goes into securities fraud pretty quickly if you knowingly put out incorrect financials and allow trading.
Free markets are not immune to panic.. a few hours break in trading that affects everyone is fair, and allows participants time to analyse whatever news release occurred, rather than knee-jerk liquidization of their positions, which they may come to regret after cooling off.
The 1929 stock market collapse was an accurate reflection of real-world economic conditions, it wasn't a panic crash and it didn't cause the great depression. There are a ton of theories about why the depression happened but pretty much none of them claim fiddling with the stock market rules would have helped anything.
Stock prices during the depression were reasonable, they were just news nobody wanted to hear.
Economists also think that WWII ended the depression.
As if flattening the major cities of every developed country except the U.S. and spending the majority of the world's economic activity on objects whose sole purpose is to destroy and be destroyed. That brought prosperity.
