How are you going to hoard "at no risk"? You're trying to corner the market for a given stock in an index pushing it's price way up and thus exposing yourself to the price crashing down and wiping you out. Meanwhile the passives are routinely buying and selling index funds depending on their need to save or raise cash so the net inflows into that stock are positive or negative depending on that. And that stock is only a small part of the total portfolio. Depending on how their specific timing works out your scheme is a net positive or negative but it never wipes them out. Your risk is way worse, particularly if you need to leverage to buy the whole position. Even if your play was to corner the market completely and own almost the full company the end result would be it being removed from the index for there not being enough float around. Then all the index funds dump what they had of it, and you lose your shirt.

I agree with you mostly, that there are spaces where active can make great bets. But this particular example isn't quite true. Passive Index funds are not automated 100% and have discretion on when/how closely they track the index. They DO have to try and track the index, but that doesn't mean they have to own every stock IN the index, nor does it mean they have to buy X stock tomorrow, regardless of price.

source: Any prospectus/annual report of a large index fund, such as VTI.