The whole point of having a trademark, is to make it obvious to the consumer that it is “your” product, not the product of some other company.
In the CUV example, how can anyone tell that an “iX” is a BMW and an “iD4” is a VW? They could as easily be different models produced by the same company.
In the “X” case, is it a different company, or a new product from “Xfinity”, also a communications company?
You are just not understanding the reason for a trademark, how they work, or what they are designed to protect. I’ll leave it at that. If the prior links I provided (perhaps you did not read them) did not help, nothing I state further will.
That is the entire point of requiring somehow UNIQUE names in various categories. The consumer should know the brand name of a trademarked product is made/sold by ONE entity only–not many different mfrs/resellers/retailers. Otherwise, brand names have no value.