Do you have a source or any hard evidence that they were the direct cause of the spike? It could have just as easily been a larger hedge fund manipulating the AH similarly to how settlement was manipulated over the past few months. However, in those cases most of the crowd was short and the VIX was manipulated down so there was no "problem".
As a Merrill Edge client I have access to BOAML's equity derivatives research. In a Feb 6 2018 report they (Benjamin Bowler et al) wrote this:
"
A “Minsky Moment” for the VIX
As noted in our 2018 Outlook, while we did not see short volatility positioning as large
enough or levered enough to catalyze the next global crisis, we were concerned about
the risk of an outsized VIX spike in 2018 with little forewarning, potentially amplified by
a short vol positioning squeeze.
February 5th delivered exactly such a VIX spike, with the constant maturity VIX 1-month
future recording its largest spike in history (by a wide margin) relative to the decline in
US equities (Chart 11). Indeed, the 94.4% rise in the constant maturity VIX 1M future
was nearly 17.5x as large as the -5.4% drop in e-mini futures, easily the largest stress
beta recorded (data since Sep-07) and a large enough percentage rise to leave some
popular short volatility strategies at risk of losing 100% of their capital.
Particularly striking was the acceleration in the vol spike between 4pm and 4:15pm
(Chart 12), when the front-month VIX futures contract rose nearly 10 vol points and the
second-month contract rose nearly 8 vol points. For context, the largest close-to-close
move ever recorded in the constant maturity VIX 1M future was ~5.5 vol points in Brexit.
A likely driver of the parabolic vol spike into the close on 5-Feb was the sizeable
rebalancing needs of levered and inverse VIX products, which by our estimates may have
bought ~$250mn vega or a record 26% of the day’s volume ($930mn vega) traded in
the front two VIX futures contracts.
Despite the pain likely being felt by some in the short vol community, it is important to
remember that the size of potential losses here is a fraction of the broader active risktaking
market. For example, even if some popular short volatility strategies lose 100%
of their capital, this would likely be several orders of magnitude less than the ~$1tn loss
in S&P 500 market capitalization experienced on 5-Feb.
Note that with VIX futures now at a significantly higher base level and the short vol
positioning embedded in “inverse VIX” products significantly de-fanged, an imminent
repeat of the events of 5-Feb becomes less acute, in our view."
Barclays (a major player in VIX products) agrees
http://www.businessinsider.com/barclays-vix-and-225-billion-stock-market-sell-off-2018-2:
'Barclays told clients that the spike in the VIX index was "technical in nature and does not necessarily indicate a true increase in risk perception."
It said the initial increase was driven by a sell-off in equities, but said the bulk of the move in VIX futures happened after the stock market close, which suggests the demand was driven by demand from VIX managers who buy VIX futures when they rise in order to maintain constant leverage.'
