There's a theory that the BCH-ABC vs BCH-SV war brought to light: that "trustless" doesn't really mean trustless. It means "trustless, as long as you trust the coin". Innately, the BCH-ABC vs BCH-SV flamewar destroyed the notion of trustless and decentralized.
Anyway, I don't really know why BTC has done so poorly here. And the correlation to the BCH-ABC vs BCH-SV war may have just been coincidence. But its worth thinking about and discussing... maybe we can learn something from the past few weeks.
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Alternatively: "Store of Value" was a self-defeating prophesy. BTC was a "good" store of value, until it lost 50%+ in just a week or two. So as BTC fell, it just fell harder and harder, as the "store of value" argument was defeated.