I also think they have sufficient career progression (in terms of problems solved and $$$ earned) that nobody feels the need to build a big team. Pure speculation though, I know nothing about RenTech except that the pay is... generous.
The incentives at rentec favor low employee counts. The main fund is both limited to insiders and limited in total capital, so every new hire is judged by how much they can improve returns, if they cost more than they improve, than they're a pure net negative.
This is different from most orgs who can grow revenue through expansion of some sort, in which case the incentive often favors adding new employees. Not to mention the tendency for people in tech to be evaluated by how many people are in their org, further incentivizing adding headcount to signify your importance.
That's one thing I find interesting about hedge funds and (some, not all) finance organizations: their ability to make huge amounts of money with small staffs. IIRC RenTech's revenue per employee is something entirely absurd, in the millions.
It's just leverage. You can leverage people, capital, technology. Many companies were built leveraging large numbers of people. Many companies leverage technology. Many companies leverage capital. Gotta lever up.
Yep, they don't have products they need to maintain. Just enough infra to figure out the next profitable trade. Once heir models stop being ahead the curve, they can be just scrapped.
Most organizations would have choked themselves on tens of thousands of bad hires long ago.