"Even an extremely valuable resource discovery there would probably only result in the bare minimum settlement needed to develop it, like an offshore oil rig or a polar whaling station."

Yes. Like say, two or three people. Coupled with maybe 20-30 people assisting via teleoperation.
The valuable resource is lunar water and lunar dirt.

If you have rocket fuel at the lunar surface, then getting to the Moon could be cheaper. Actually, if the rocket fuel is just on the lunar surface, then leaving the Moon is cheaper.
If you can transport lunar water or rocket fuel to lunar orbit, then getting to the lunar surface is easier/cheaper.

To be cheaper, the lunar water must be sold at a reasonable price. If lunar water needs to be sold at say $10,000 per lb, then it's not going to be cheaper. If electrical power on the moon is $500 per kw/h then that's not cheap enough.
If there is enough demand for lunar water [and there is minable lunar] then you can lower the cost of lunar water.

Suppose, you had company that wanted to sell lunar material to Earthlings. And the target price was 50 to 100 dollars per gram. Though this company was going to sell the material by the ton to vendors, so say 50 million per tonne, and wanted to sell 100 tonnes per year- 5 billion dollars per year.
So, the company needs capital, to do this it needs to enter into contractual agreements with vendors. The agreement could be that company will only mine at most 100 tonnes of lunar material per year for next 20 years.
It will only be able to mine few tonnes in the first years or so, but will sell the first 10 tonnes at $100 per gram, and will sell at $50 per gram when producing more per year. If any vendor will agree [and pay a small percentage of total order, say .001%] they will get exclusive rights to buy at a certain price. This prepayment will be made at a point the first rocket successful launches- it's basically a future option to buy at that point.
So, with say amount totaling 100 tons lunar sample of these agreements but with no money being given yet but simply agreements that a small amount of money will be given when the rocket launches, then the company gets venture capital money, and perhaps after getting venture capital, 2 or 3 years later, they have a rocket on the pad.

Before all this, one needs to know if there is minable water on the Moon. If it is determined that there is minable water on the Moon, then a lunar water mining company needs customers for the water when it is mined.

The lunar dirt miners need rocket fuel. It would willing to buy rocket fuel at lunar surface and at lunar orbit [and LEO- but different story] if at a low enough price.
So, what is needed is a company that will build and operate a gas station on the Lunar surface. The same company or a different company could run a gas station in Lunar orbit.
A gas station on lunar surface is useless without having water [or rocket fuel to sell], it needs to be able to buy lunar water at a reasonable price, so it enters into agreements with lunar water miners, and lunar dirt miner who will be one of their customers for rocket fuel.
Etc.