When market conditions change people are usually positioned for the past 10 years and think that this can continue into the future.
If we know that Powell wants to be Volcker 2.0 we can assign probabilities of outcomes as follows:
Period Like The 1970s: 10%
Period Like 2000-2008: 30%
Period Like 1929: 60%
The reason i believe the 1929 period is the most probable is because nobody thinks it can happen again. As well as the fact that we have created the largest monetary policy bubble in US history. Given the historically cyclical nature of markets and humans, the odds that something like 1929 happening again almost exactly 100 years later, are high.