"The final nail in the Keynesian coffin?"

I'll say no. Have politicians ever let evidence stand in their way of consolidating power and increasing spending? Cato's Dan Mitchell is also skeptical but points to one academic - Professor John Cochrane of the University of Chicago:

The tide also changed in economic ideas. The brief resurgence of traditional Keynesian ideas is washing away from the world of economic policy. …Why? In part, because even in economics, you can’t be wrong too many times in a row. …Our first big stimulus fell flat, leaving Keynesians to argue that the recession would have been worse otherwise. George Washington’s doctors probably argued that if they hadn’t bled him, he would have died faster. With the 2013 sequester, Keynesians warned that reduced spending and the end of 99-week unemployment benefits would drive the economy back to recession. Instead, unemployment came down faster than expected, and growth returned, albeit modestly. The story is similar in the U.K.