I actually see it as being rather simplistic to assume it's a symbiotic relationship instead of a parasitic one. Parasites can often implement methods to make themselves attractive or initiate the parasitic relationship, precisely, because it is mostly in their own main interest.
We just recently saw the owner of the Klippers expose that same relationship, just because something is on a far larger scale, does not mean that it is any less the same thing underlying it. Yes, _some_ founders get insanely wealthy, but the VCs get even wealthier because they have fine-tuned a formula of exploitation and manipulation. Yes, a lot of investments they make go bust, but that's why they take an arm and a leg and a pound of flesh while they're at it. They are essentially diversifying their investments, but they are also profiteering from a huge arbitrage opportunity. They are essentially trading in the inefficiencies of the market because that is risk they don't want to burden and don't really actually want to do any work to do due diligence to find the good investments. They are in the business of statistical investment..... the more money you throw at it, the higher the likelihood of hitting the bulls eye....simply based on statistical probability.
That is of course offset by various other revenue streams because the scale is not frequent enough to base it purely on statistical probability, but that is the core.