Well, that is what markets do: behave. Rationally or not.

The 1929 panic was also irrational but it happened. There is no way to solve that.

Panics happen and bubbles too, and in the meantime, very long term investments tend to grow (in average), as long as the economy works as expected (improving in average, long-term).

Of course, catastrophes are not impossible (the Black Death, the French Revolution, World Wars...).