Soaking chains is an old-school practice that isn't very practical.
Fluid films, be they grease or a thinner oil, need to be replentished, as they will be slung out of the friction areas real fast.
So, many would use a thicker grease or oil and soak them so the lubricant could penetrate into the friction areas. Many even heated the oil.
The answer by most chain lube co's was to start adding tackifier to the mix, which does indeed keep the fluid there longer, but it also brought other problems to the table. Such as now being a great attractor of dirt and grit, which will eat a chain fast.
Many times a chain lube will have a solvent as well as a tackifier, and the solvent helps the mix to "set-up" real fast. Problem is that these type lubes could set up on each side of the reel, at the pin/bushing openings, before the lube actually penetrates all the way across the pin/bushing area (many times creating pressure in the middle keeping the lube on both sides pushed out). Leaving you with two clogged ends, and a great place in between for wear to occur. Not to mention the great dirt magnet, and the fact that the tackifier itself takes up precious room for good lube.
Another big problem was the mess these type of lubes create. You riders know exactly what I'm talking about here. It is real tough to get some of these lubes cleaned off your bike and its parts, including the chain itself.
Many times this hassle would keep riders from providing the level of cleaning and maintenance that they should.
Many would go back to the old motor oil method, especially since many manuals even today recommend using a 90wt gear oil or similar fluid for the chain lube.
Problem is, a fluid film must maintain at least .001" of thickness between the mating parts to be able to protect from wear. Once this film has been depleted, there is precious little boundary additives in the small amount of fluid to continue to protect.
This depletion also occurs in just a very few revolutions.
The answer is to use a barrier lubricant.
Dry-films are basicaly a solvent base carrier with a massive dose of barrier lubricant, such as moly (MoS2), or other chemo-absorbable products.
The light solvent carrier will evaporate soon after application, leaving these polar solids and chemo-absorbable materials adhered to the friction sufaces of the chain.
With such a barrier lubricant in place, there is no need to maintain a fluid film between the parts, as the lubricating materials are now residing at the oxide layer of the metal, and ready to perform when heat and load present themselves.
The polar nature of these materials also helps them to stay in place, and resist washout, MUCH longer than any fluid film type product can.
And as there are no tackifiers to make a great mess, cleaning of a dry-film is as easy as a wipe with a clean rag.
There are a few "dry-films" that will actually be completely dry once the carrier has evaporated, but with the use of elastomeric sealing rings in some chains, dry-films that are designed for moto use will also have very small amounts of oils in them, which will normally not let the fluid "comletely" dry out. This is designed to help keep the sealing rings supple.
Semi-dry-film would probably be a more correct term.