Bringing Samsung in as a 5G supplier is a classic Cook move. The objective to create an internal market with a major and a minor supplier should force both to offer competitive pricing (with the assumption that the volume of an Apple purchase makes up for the smaller margin). That’s a risky call given the new supplier relationship.
It’s also a pretty standard play from Apple, and it’s one that anyone paying attention will have seen in other areas, such as screen display technology and memory chip supply. I’m pretty sure that Qualcomm has been paying attention and are expecting such a move from Apple and that the long-term contract with Apple will have a number of stops in the terms to block this game-playing. Apple needs Qualcomm a lot more than Qualcomm needs Apple at this stage.