The financial authorities do their best to keep an eye on things. If there are signs of turmoil in the markets they try to intervene with liquidity or whatever to buoy things up and smooth things out.
Often a market crash can, in hindsight, be attributed to what’s called “black swan” (dramatic, unusual, unexpected) events or factors. In 2000 it was the out-of-control Historic Tech Bubble. In 2008 it was the scandalous Sub-prime Mortgage Crisis.
In 2022 it might be the Great Crypto Crash.