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I don’t believe this is correct.

My understanding is that these automatic limit down rules were added in response to the flash crash in 2010, during which the Dow Jones lost 1000 points over the course of minutes.

This is incorrect, it was somewhere during/after the 2008 recession that these circuit breakers went into effect (because I remember they didn't exist at that time)

not exactly - circuit breaker was put in place after the 1987 crash, but the 3-tier system (7-13-20) went into effect only in 2013: https://www.wikiwand.com/en/Trading_curb