that's maybe a reasonable comment re: their minority holdings in other public companies. but they have other business activities apart from their minority hold

that's maybe a reasonable comment re: their minority holdings in other public companies. but they have other business activities apart from their minority holdings, which you're ignoring. they're also able to identify opportunities to take over (both private and public) companies entirely, and add value to those businesses in an active way that a small private passive investor is not able