IIRC, in Sonic X (not a great reference, but whatever) they said technology in Sonic's world was far more advanced, and there they could build machinery very fast. As long as Robotnik had some blueprint data and resuorces, he could build those places very quickly. Let's say death Egg already had everything he needed to work there with no incidents.
https://twitter.com/CFWhitehead/status/902946335434825728 This tweet alone makes the topic of Chaos Emeralds really interesting. What makes them "drift off" back into the special stage dimension? More importantly, why do they keep ending up there? It'd be cool to figure out more about the emeralds, especially with stuff like this. It makes me think that there is an established lore to the emeralds that's all behind the scenes, maybe similar to the Castlevania timeline previously being only used by developers, but then made public. No idea if that's a good way to look at it or not. Makes you wonder if technology is so advanced, how come he made Decoe and Bocoe so stupid? :v:
Decoe, Bocoe, Orbot, Cubot... Robotnik nees to feel everyone's an idiot around him and has to do thigs himself to do them right. He could also be boycotting himself unconsciously to enjoy more adventures against Sonic.
There are two ways to look at this: 1) It's long since been a thing that the Chaos Emeralds are basically Dragon Balls. What happens when you use the Dragon Balls? They scatter, far and wide. It's not inconceivable to think that they're basically doing the same thing here but given the chaotic nature behind them and that they're effectively from another dimension, they're merely returning back to their natural state - the things have a lot of power, y'know. 2) An excuse for them to be in special stages for the player every game. Your call =P
I for one view it in the Dragon Ball schema. If anything, it could justify the island-hopping for the Genesis titles, by nature of the emeralds only being accessible in the next island. You could even take into account gameplay mechanics, in how you can't access a special stage from the same entry-point twice, so you have to keep moving along to collect them. You could also scratch the need for island-hopping and attempt to integrate the Game Gear titles. The Genesis titles island-hop because Eggman keeps moving on, possibly in an attempt to get an advantage over Sonic, but in the Game Gear titles Eggman continues to pursue South Island. He just covers a wider range of the island, and finding more access points to the special stage because of it. Now if acccess to the special stage doesn't switch between islands, and is just accessible once each from the many access points scattered around them, then I wonder what the "true" special stage would be?