A crash is a market realizing it had been wrong about something, yes. Or, a "crash" as defined a dramatic plunge rather than a downturn over time is usually so

A crash is a market realizing it had been wrong about something, yes. Or, a "crash" as defined a dramatic plunge rather than a downturn over time is usually some kind of feedback loop where prices falling creates expectations that prices will drop even further and so on, often if the market is mostly driven by greater-fool-theory herd behavior.