My understanding is that they got several big donors to supplement Sitake and Detmers salary. Apparently Detmer's was so much that there just wasn't enough for assistant coaches, which is why they got what they got.
I think you are going to see serious push back in expanding that salary even more... considering they just opened it and look at the results. The problem is, they hired poorly again, which is the BYU way since the first qualification is religious status and membership.