CBA shares - new normal ?

The 25 times earning multiple is extreme. Yet it’s held this price for almost 3 months indicating a level of comfort for investors to hold at such a sky high valuation. I think this is significant as it would represent a major attitude shift in the countries investment community. For decades the general rule of thumb is around 15 times earnings is reasonable for a bank. Yet in the last year this sentiment has been binned in favour of a willingness to buy at a 25 times earnings. And as the nations biggest company it could set a precedent in acceptance of lower returns and dividend yields among the entire ASX. Other bank stocks are also following CBA to sky high prices with the yield on offer going lower each day. Banks have always been the main source for dividend investors.
Does anyone body know why our bank stocks, keeps going up, even when the consensus is earnings growth will be modest, if at all. I cannot fathom it. $CommBank (CBA.AU)$