Right, "savvy investors", mostly professionals, compete with each other to be first to set the market prices at their truer values. The index investor just goes along for the ride.
> then the index rebalance forces index fund investors to buy in
That's not really how it works for cap weighted whole market indices. They remain cap weighted as prices change, there's no need to "buy more" of a winning stock, you already had the stock, it won, now you have more of it (in USD terms).
> then the index rebalance forces index fund investors to buy in
That's not really how it works for cap weighted whole market indices. They remain cap weighted as prices change, there's no need to "buy more" of a winning stock, you already had the stock, it won, now you have more of it (in USD terms).