'Now you know': Why the Fed feared a quarter-point hike

What's next for the Fed? Five truths for 2016

For years, one of the great market mysteries was why the Fed was so reluctant to enact a seemingly innocuous quarter-point rate hike.

Mystery solved.

Since the U.S. central bank began an incremental tightening of monetary policy, particularly over the past 15 months or so, markets have been all over the place, economic growth remains muted and the world has become a scarier place.

That modest Fed move, then, is looming large.

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"Now you know," said Nick Colas, chief market strategist at Convergex. "You have to put the last week into context. This has been going on in a progressively more volatile way since the beginning of last year."

Indeed, while stocks have gotten clobbered to start the year, the market has never been the same since the Fed ended quantitative easing in October 2014. The monthly bond-buying program added $3.7 trillion to the Fed's balance sheet and helped jolt stocks to a surge of more than 200 percent since the March 2009 recession lows.