I have no quibble with your premise, but why was Mika's commitment soft? I'm suggesting BYU's on the field struggles, Utah's on the field victories, and Utah's P5 opportunities certainly impacted his decision making.
In addition, Tayler Katoa chose USC because of the tremendous undergraduate AND graduate benefits offered him. Utah was his second choice. Maybe there was nothing BYU could have done to change his mind; however, if BYU had been ranked in the top 20 for multiple years before Tayler made his decision, BYU's success may have moved him to become a Cougar like his parents.