I was working under HDThoreaun's assumption that the margins would be lower.

If they have other opportunities for investment with higher margins, they should seize those, of course. And perhaps even call up investors for more capital, if required.

When the agents employed by investors would be harmed by releasing capital back, which is guaranteed since so many people’s compensation is in the form of stock and returning capital leads to decreasing stock value, why would those agents ever return the capital voluntarily?

Have you heard of stock buybacks?

Buybacks increase stock price. Nvidia has a tiny dividend but most shareholder returns are in the form of buybacks.