The reasons why markets were at such dizzy heights is simply because of the previous banking crises where billions were dished out and QE is with us to this day in many of the G8 countries.
Pretty much all countries are just announcing further 100s of billions of money.
All this cash will have to be spent or stored in some place or other.
Given banks and gilts offering 2% or less, the natural home for cash becomes the stock market with companies paying 3-5% dividends or higher.
House price inflation has gone high enough and there isn't really anything else to store value.
I do see a V type correction and stock market making new highs once all those billions get injected into the global economy.
Just my tuppence.