1. Economically it is probably the right move for UFC - gives Ronda a plausible path to reclaim the title. The fight will sell well. The old rivalry will be rekindled. Both Tate and Ronda will promote the hell out of the fight. And - when people have time to think it over - they will realize that it will likely be one hell of a good fight. The winner can then fight Holly. Another big payday fight.
2. UFC feels some obligation to Ronda for her tireless promotional efforts and less obligation to Holly because she refused to "wait" for the Ronda rematch as they initially requested.
3. In terms of street justice, it seems a bit unfair. Holly gave Meisha a closer fight than Ronda gave Holly. Holly could very well beat Meisha in a rematch. Holly is "nicer", more respectful, more dedicated to the sport. But Ronda was the champ much longer, had more title defenses and dominated WMMA (at least at the 135 pound level) for nearly 4 years, not 4 months.
4. UFC has to think through how to manage this troika. My guess - they give the first shot at Meisha to Ronda but they are not going to wait forever for her to come back - a deadline of November at the very latest. Then the winner faces Holly. If Ronda loses to Meisha and Holly beats Meisha, then Ronda gets another shot at Holly.