There's gotta be a clear O.S. benefit they saw as well. Merck's recent comments pretty much clarify they have everything to meet primary and secondary endpoints.
Rida's very likely superior performances in the largest(softtissue)subpopulations(reviewed here ad nauseum in the past) have to bolster the case for overall approval.
In addition, once that happens, it's likely to supercharge the development and acceptance of Rida in other indications.