To be fair, a lot of megas seem to overlap each other. When Shiawase's "thing" is (and I quote the Core Rulebook) "Shiawase has its hands in nuclear power, environmental engineering, biotech, heavy industry, technical service, minerals, military goods," and S-K's "thing" is "heavy industry, chemicals, finance, and aerospace with a presence in many other areas" it starts to run together.
SpinGlobal though...a friend of mine made the joke-that's-true, "SpinGlobal is 50% the entirety of Global Sandstorm and 50% Johnny Spinrad himself, the rest of Spinrad Industries was a rounding error."
Aside from his overwhelming ability to grab the attention of everyone in the dang world, Johnny's business has always been catering to (and fleecing) the elite. From Omega-level clinics to his insanely over-priced commlinks everything about Johnny Spinrad is about the neo-royalty of the 6th world. The Incorporated Caliphate is a perfect springboard for that, being a merging of royal families, religion, "divine right of kings" and overwrought opulence.
Meanwhile his "cyberzombie without the penalties" augmentations challenges Evo on it's home turf, his positioning geographically reaches into Wuxing and S-K's zones, his sheer PRESENCE as a public figure pees on Horizon and Aztechnology's territory, and having access to fanatics in large numbers is equal to any reputation of having scary or impressive paramilitary groups like the Red Samurai.