Shamelessly plugging an old article of mine. But there are a lot of similarities with today’s situation. Quoting my past self:
In financial markets, expected returns are your compensation for taking on market risk. In other words, high expected returns protect you from the unexpected. But when the crowd piles into your trade, expected returns go to zero at the same time that the probability of a major price decline increases. So your protection goes away at the moment that you need it most.