The stock market is not the economy, Wall Street is not Main Street. You need to look at this more macroscopically if you want to understand this.

Basically: China tech sector just made a big splash, traders who witnessed this think other traders will sell because maybe US tech sector wasn't as hot, so they sell as other traders also think that and sell.

The fall will come to rest once stocks have fallen enough that traders stop thinking other traders will sell.

Investors holding for the long haul will see this fall as stocks going on sale and proceed to buy because they think other investors will buy.

Meanwhile in the real world, on Main Street, nothing has really changed.

Bogleheads meanwhile are just starting the day with their coffee, no damns given to the machinations of the stock market because it's Monday and there's work to be done.