For example, it likely didn't really rain 24/7 ~everywhere on the planet for ~2 million years straight, but, that was my initial picture upon reading what you said. I said out loud to myself, "wow", and then read the article you linked.
Rather, it seems more like: over that period of 2 million years, across the exposed land mass of Pangaea (which was large, but only covered ~1/3rd of the planet) the climate was overall much more humid than most places are today, and it likely rained often.
That is not anywhere near as absurd to imagine, though it's still pretty darn cool.
Transport costs Moon-surface -> Earth-surface are ... non-intuitive to say the least.
People might ask why do that at all. There are lots of metals in space in concentrated form, solar energy is uninterrupted, and if a large part of your market is off earth it starts to make lots of sense.
Not anytime soon mind you, but one could imagine a future like that pretty easily.
[Assuming people invest in infrastructure], In the mid- to long-term you might be able to ship goods to earth from a moon based factory cheaper than you could from some earth-based locations.
This isn't really anything special about the moon either, mind you. It's the facts that:
* In comparison, Earth has extremely strong gravity;
* Gravity effects compound.
To get some intuition, look at a Saturn V. https://upload.wikimedia.org/wikipedia/commons/b/b2/Saturn_v...
To get to the moon from earth, you need the whole thing. To get back, you just need the top half of the lunar module (to get to lunar orbit) the service module (to get to reentry) and the Command module (to survive the reentry). A tiny part of the entire assembly!
(purists might point out that the system could be rather smaller if there was no intention of a return mission... which is fair enough. It's just to get an initial intuition across here!)