Why do equity investors seem so nervous?

Since the spring and especially the autumn of 201 8 , share prices have fallen sharply in the United States and the euro zone even though companies' fundamental situation is still very good. Why are equity investors so extremely nervous? Because they remember that in 2007 also companies seemed to be in a good situation; but fundamentally, it is far more solid now, thanks to low interest rates and high profit rates; Because the risk limits that investors set for themselves are very severe, forcing them to sell quickly if share prices fall ; Because there is a growth slowdown and an investment in cash is not very disadvantageous .