I didn't say you should invest in companies already with a big market cap. I said market cap increasing is the ROI to investors (besides dividends, which is mostly irrelevant when investing in tech companies).
That's exactly how startups work. You invest at a cap of $50m. Its market cap increases to $1 billion. You just made 20x (provided you have liquidity).
Completely wrong. Hint: You are on HN. Startups obviously don't start at a large market cap.