A stock market crash can be a manipulation made by smart players to buy good stocks at cheap prices taking advantage of small investors who panic and sell.
Invest only in companies which rise in long time (top USA stocks) and don’t sell the stocks even if market crashes. It will rise more than before the drop, as proven by historical charts.
Other stocks are vulnerable, they can drop if the company make frauds.
A cheap price is only an opportunity to buy more.