Every. Single. Time. Valuations too high. Debt too high. Equity too low.
I am pretty cynical because I have read a bit too much history and seen this so many times working in investment management but...so what? Some rich people lose a ton of money...okay? Capitalism has losers. You lose.
Also, in the last crisis, a ton of people (particularly Blackstone) made a ton of money buying huge deals at the very top of the market. None of this excess came out of the market. Lots of people who borrowed tons of money were just able to take their paper to the Fed, and keep playing.