> IF that is the case why have stocks and shares gone
> soaring up after Trumps victory, are shareholders
> irrational?

In general, it's the margins. From the outside, the effect is that of a bunch of headless chickens; inside, every individual stockbroker (and more to the point, every individual quant's computer program) is attempting to game the system. Playing the stock market is horseracing for posh boys, all with other people's money.

In this particular case, it's party time for the wide boys.