Since I too am greatly entertained by NukeNES and CarmenNES, but haven't said anything, I'll bite.
Before I do, though, I just want to make one thing clear: you want to call it fun? Fine, it may be fun. You're entitled to that by all rights and I won't criticize its existence if people enjoy it. It's serving a function in a hobby, and that's reasonable.
But defending it to any capacity at all for being realistic though is an entirely different ballgame. Neither NES is realistic in the slightest, and trying to pretend they are or saying "Oh, well, things could just be different, and stuff" is just rationalizing an excuse for them, and a mighty bad one at that. If the counter was "Well, it may be silly, but I enjoy it," that'd be a fine enough one. But trying to justify some of the things that go on is a fool's errand, as we shall see:
Yeah. That's unrealistic too.
Um, whut?
Changing a PoD back in 8000 BC or something does not make Lake Victoria suddenly sprout gold mines or make Middle Eastern wheat spring up in North America to miraculously feed a much larger population. Resources do not suddenly change unless you ignore them or you alter them too and then decide not to tell anyone.
Hrm, lets see: because it wasn't actually rich in material terms? Most of their gold was imported. They mostly had jade and obsidian which they exported for things like gold (mostly from Panama). They didn't have much in the way of material wealth as we define it. If you translated the Mayan kingdoms to NESing, there likely wouldn't be four trade centers in the Yucatan, particularly as they were mostly a village-state and the "cities" were chiefly ceremonial...
Onto the actual case in point, Lake Victoria is extremely susceptible to climate change, would probably be over-fished if it had to support the extremely large population densities required to sustain 4 ECs around it, and lets not forget: there's pretty much nothing around it. Uganda has some copper and cobalt, of which only the former is usable in this time period, and both of which are somewhat inaccessible due to a lack of mining technology. Tanzania has ivory and gold, but most of those are centered more towards the coast than the uplands.
So what exactly are these people trading between themselves (as boat travel all the way up the Nile is rather hard, not being accomplished by Europeans until 1858)? Who knows. Might as well be a nuclear weapon based economy. Maybe the Russians taught them the secrets of teleportation.
Most really rapid colonization fits in the context of industrial settings, though there have been some other cases, like parts of ITNES or STKNES5 (then again, vaunted as that NES was, NPCs would just roll over and die at the smallest poke, so expansion was fairly easy--I could have colonized the entire Pacific rim by 1000 BC at the rate I had been going if I'd stayed). That said, those Russians are pretty crazy too.
Somehow, they're Russians despite the fact the people there at the time are Scythians or proto-Slavs, since the ethnic makeup of that area is almost entirely a product of the several waves of human migrations starting from around this time forward for the next half millennium. Then, on top of that, they're named Russians, despite the name coming from the Rus, a group of Vikings who didn't show up around 800 AD (lets not even get into how Scandinavian despite its really horribly broken up geography is already an empire). But they're still Russians. Somehow.
And they managed to conduct Russia's expansion from the Ob to the Pacific in 100 years, when it took the real Russians, with vastly superior technology and organization, about the same amount of time... 1600 years later. When there are Huns and Xiong-Nu and Proto-Turks and what not going the other way. Makes sense.
And they attacked Austria. Which also magically sprang into existence.
Then there's your Hadic Empire. Which somehow controls the Ukraine from Egypt, and also holds on to the Sudan, despite the fact it would be at least ten times as hard to administer as the similarly sized Roman Empire due to much more difficult terrain, disconnected waterways, and the extreme difference in climate and latitude, particularly when the most advanced method of overland transportation at this time is a paved stone road... and the Ukraine can't be farmed and is of limited economic value at this point considering the state of agriculture... but it and the Caspian have still got six ECs. Somehow.
And the Amazon is ruled by a single government. Again, somehow. Despite there being literally thousands of different tribes in the area it encompasses. Same thing with the North American tribes... which somehow arose before the Mesoamericans or South Americans despite the utterly massive disadvantages...
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Most heavily guarded airspace in the world? Easily infiltratable by amateurs with helicopters. Particularly when the government should be highly paranoid of terrorist attacks given somehow two megatons of conventional explosives was detonated on the Golden Gate Bridge.
The Mafia. Tanks. L'Mao!
Yeah, because illegal internet gambling, drug trafficking, money laundering, cyberterrorism, all of that isn't far more profitable than wasting money on getting military grade weapons for conquest, engaging in said conquest, and then paying the massive overhead costs to maintain territory and defend it against, you know, the United States government. Flagrantly attacking a city also keeps well in line with the Mafia policy of operating from the shadows and minimizing risk...
Because France launching nuclear strikes and all of Europe's major powers being involved in a land war when their major trading partners are each other certainly wouldn't have done that already.
Yeah. Because those advances would totally necessitate the basic infantryman stand in some hole in the ground. Instead of, say, I don't know, dropping telephone poles made of tungsten onto those amazing static weapon systems from space. Or dropping a metamaterial sheathed nuclear warhead or something on it. Or deploy massed waves of air and land UCVs. Or, or, or...
No, the technology of 2107 requires men stand in trenches with guns.
... and hasn't apparently advanced much at all beyond the projections of 2012 or so.
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Justifying these things is just wrong. Don't do it. Say "I'm willing to overlook this for the sake of having fun" or "I'm willing to suspend disbelief to enjoy this experience regardless," or something other than trying to justify it. Please. Doing the latter makes me want to jam q-tips into my brain.
It's like how Doc Ock in Spiderman II was somehow a genius at nuclear physics, robotics, programming, and artificial intelligence, but was too stupid to build a robot to handle the fusion reactor automatically, shield it, or deploy it in a building not made of metal when the thing operated on magnetic fields. Or how the fireball didn't instantly flash vaporize the entire East River into steam or cause a nuclear meltdown, but simply sank. Or, or, or...
Nobody justifies those things. Some people say "Ghost Rider was stupid and unbelievable," and other people respond "It was a movie about a guy whose head caught on fire and who fought crime with magical chains; what did you expect?"
Be the latter guy.
It kept falling apart, and occasionally wasted lots of resources and potential on the ultimately-senseless and wasteful southwards conquest. A legitimate case could be made about Egypt's control over Sudan being one of the primary causes of Egypt constantly getting, for the lack of any more fitting term, completely screwed over on and on and on like few other nations in NESing history.
