XIV collapse was caused by an unprecedented spike in the VIX index.
"Volpocalypse" was indeed an unprecedented spike in IV, which the futures market was reacting to. Seems pretty different to me than the classic short squeeze scenarios of GME or Volkswagen.
This collective price response wasn't a short squeeze, but instead it was closer to a gamma squeeze. It didn't rely on finite supply of any security, just limited liquidity and trade sizes large enough to move the market price.
The XIV collapse happened on the largest single day percent change in VIX history. It’s a bit silly to say it was the only the futures but not the literal index they track.
Because those of us who have extensive knowledge of volatility products (I was a specialist in VIX options at the CBOE, the first to make markets in VXX, and one of the largest traders in volatility ETF options over the past decade), believe that the spike in the VIX index was caused by arbitrageurs reacting to a spike in the VIX futures. And VIX futures were simply reacting to the order flow caused by the daily rebalancing of leveraged ETFs.
What research have you done to show evidence otherwise?