Qualcomm had the option to not submit their patent for use in the standard. The thing about standards is that they are, well, standard so everyone who wants to make something compatible has to license all the patents that make it up. FRAND requirements are used to keep the cost reasonable. A company could not include their patents but then they might just be able to license it to a handful of companies for whatever thousands or millions that company is willing to pay. On the other hand, if you get your patent into the standard you might only get, say, $0.50-1.00 per device but you're getting it for tens of millions of devices so you end up making a lot more money in the long run.
Qualcomm agreed to the FRAND terms to get their patent included and now that they have a virtual monopoly on the technology they are trying to renege.