Not speaking of any particular studio at all, here:
Studios assign territories to licensees. They have different offices/divisions all over the world.
Why license a valuable property to just one company when you spread it around, right? One operates/sells in Asia, one takes the US, One in Europe, etc. Plus, some properties are simply more popular in different parts of the world. Some things can and can't be offered for any number of reasons. There's no real 'one thing'...
It's made pretty clear up front, there is no exclusivity. BUT, most studios make a sincere effort not to cannibalize a given property by offering different categories, price points, that sort of thing. We're generally known for 'High-End' replicas and enjoy that category. Some are known for plush, toys, poster, etc. This is why you see some companies selling similar items. There's almost always a difference in price, materials, etc. Sometimes not. Like I said, most make the effort not to have too many companies doing the same thing. Still, it happens.
All the more reason to be an educated consumer. Look around, do your homework...see how many flavors of 'whatever' is being offered before you buy!
Now, none of this is to say one can't have global rights to something. It's just be less common with larger studios/franchises.
Apologies for the word salad. Just making the effort not to single anyone out.