J.P. Morgan on Wednesday’s late day sell-off:

“market volumes are light and it does not take much to get this market moving… especially considering that SPX flirted with ATHs today.” As such, once market makers and traders realize that today was nothing more than a successful attempt to take advantage of a massively overbought market, and let out some of the air that had hoped to accelerate the gamma squeeze into a full-blown year-end meltup, the result will likely be an even more zealous attempt to ramp risk higher especially since selling like today perversely validates – and reinforces – the Fed’s “dovish” pivot, thereby making even more aggressive buying the most likely result…”