Passive investing isn't zero sum - it's positive sum. If you could buy a fraction of earnings from every business in the economy (i.e. both businesses that currently exist, and future businesses that are founded in the future), then you get a rate of return that is roughly the growth in GDP.
Concentrated portfolios are also positive-sum, and have returns higher than passive investing if you are smart or lucky.
Concentrated portfolios are also positive-sum, and have returns higher than passive investing if you are smart or lucky.