In the end, pls allow me to say, the Fundamental Reason why stock market can not go down is that stock markek's going down is Not Good for everyone, the individuals, the corporations, the US economy, the world economy. So it's a lose lose lose lose situation. That's the reason why you Always see the market go up. That's the big picture, you get it?
Just another example, if you open the chart of s&p since it was tradable, you will see regardless there were some corrections on its way for some years, it always goes up. Because on this planet, nobody wants the market to go down. You get it? That's the answer I have thought about why the market always goes up for a long time.