But what’s the point in investing in all that just to still pay hefty licensing fees in the end .... go all they and develop a superior chip
The point is that at the END of the process
(a) You can have a more performant device. You can use lower power by moving the logic onto the SoC (right now it's a separate chip on the PCB). And if Apple chooses to prioritize performance over area (like they have done with their CPUs and GPUs) you can devote more area to things like Viterbi decoding, which translate into higher performance.
(b) You can save money. Yes, whatever you do you owe QC royalties. But right now, you're ALSO paying QC to buy those modems. If you make your own modems, you're not paying QC that money, and it's not costing you as much if it's just another 10% or so of the SoC die.