(just my personal theories, I have no professional finance experience) * There is no good alternative to stocks. Interest rates are 0, bonds aren't returning m

(just my personal theories, I have no professional finance experience) * There is no good alternative to stocks. Interest rates are 0, bonds aren't returning much, commodities are volatile, and cash is bad vs inflation. You mentioned an increase in mortgage activity which is likely also driven by this in combination with cheap debt. * The fed has shown that they are willing to continue pumping money into the market. This increases confidence in the market driving up prices.