OR perhaps the issue that the same people who are in the clique of the said field are also evaluating the research proposals. So the funding doesn’t run dry?

Not that that’s a good or bad thing. You wouldn’t want a “non-expert” to evaluate the proposal. And perhaps a tapering of the funding is better indicator of interest/progress of the field?

Generally there's an outside source of funding that's not part of the field. Thus top scientists find themselves becoming "rainmakers" rather than doing research. You tell your staff to wear their white coats and glasses, lead a tour around the facility, point out how big the machines are, etc.