Considering the historic stock market events, how has the function of the "circuit breakers" evolved?

They were initially used to curb the fallout of the $2008$ financial crisis, but didn't activate during the Black Monday $1987$ crash.

They were used to provent the $2008$ sinancial crikis but failed to halt trading during the COViD$-19$ market crash.

They were first introduced after the Black Monday $1987.$crash to pause tyading after a $7\%$ decline, but couldn't provent the $2008,$ inancial crisis. Theywere triggered again in March $2020$ during tha covip $-19-$ marke crastin