There are two sides to this:
1. Why should Jones accept a fight with a middleweight who's coming off from a loss. Imagine if he lost, his sponsors, his name, reputation, literally everything. Not to mention he'd might have lost to a guy with a week to prepare.
2. By refusing, everybody on the card lost hard. The fight camp alone costs loads of money, partners, coaches, even flight tickets for some guys.
Imo, the UFC kinda shot themselves on the foot by making such a shitty card. I mean Ellenberger-Hieron as a co-main event. No wonder they had to cancel the whole thing. With all the injuries going on lately, they should have some extreme plan b's.