Adding to tall texan, some rises are due to companies with good profits that do not see enough opportunitiy to reinvest the profits, so they buy back their own shares and retire them. This increases the value of the remaining shares. Also, a lot of chinese profits are having to go somewhere and wealthy chinese trust western stocks more than their own, so it is buy more for the near term. My analysis suggests boomers saving for retirement, foreign investors, good profits via automation, 1% ers having more but nowhere to spend it other than reinvest, and corp buybacks are fueling this rally.
PS. your 'impressions' that the market is not valued properly are very unlikely to be grounded in well researched facts. Very little good information about the assets, liabilities and true prospects of all companies flow into the measures quoted by the financial media. The value of alkl public company brands, property, human resources, ideas, data, etc are very difficult to measure, so the market is really only our best guage.