By "fundamental view on the market", I mean those who have done research and know that the price of something is under- or over-valued. These are generally know

By "fundamental view on the market", I mean those who have done research and know that the price of something is under- or over-valued. These are generally known as informed investors. When they decide some security/commodity/etc is mispriced, they will immediately put a lot of money into that idea, ideally (for them) before the market adapts. With HFT, the market adapts a lot quicker than before, which is better for general investors (who are uninformed investors) as they get a price that's closer to the real value. Index funds don't have a view on specific securities. They don't perform research to try to get an edge. Instead, they believe that the market is generally efficient, the and they try to lower risk by diversifying across a large portfolio of somewhat related securities, and get a return that closely matches the overall market. As such, HFT helps them by givings them better bid-ask spreads and also providing prices that are closer to the actual value of an asset. Note that those performing fundamental analysis and buying millions of dollars worth of assets aren't SOL. They just have to be smarter about how they execute.