Let me give you a possible window into Dana's mind. Every tennis slam final that one or both of the Williams sisters played in has gotten better US TV ratings than the corresponding men's final.
Different sports, but the common idea is that Americans will watch women in individual competitive sports, IF they are stars, and IF it's for a championship. I don't think, near term anyway, the UFC has a division here. But they do have a star, and they do have a championship. And if this sells about as well as the average UFC event, he'll keep at it.
It doesn't matter if you like it or I like, as long as ENOUGH people buy the PPV, for whatever reason. And if they are people who were NOT buying the UFC before, that's an added bonus.
It's all about the money.
It's a short term cash grab, however, it is far from sustainable. It would not shock me at all to see the division dissolved by next year. An upper echelon of female fighters encompasses about half a dozen women. They have two stars, one in an inactive/retired Gina Carano, and the other Rhonda Rousey, and one badass in Cyborg.
The sports of tennis and mma are entirely different that I don't think a reasonable comparison can be made. Tennis has been around forever, and was one of the earliest sports to be commonly accepted for women to competitively play. There have been a number of female tennis stars such as Martina Navratilova, Billie Jean King, Chris Evert, Steffi Graff, and Monica Seles that helped pave the way for the Williams sisters. WMMA just does not have the benefit of having a strong talent pool.
MMA is a combat sport, tennis is not. There is a reason that the HW division tends to dictate the success of combat sports, spectators want to see the biggest and the baddest, and the girls just aint gonna provide it. Lastly, tennis provides a broader sex appeal. Most men don't find bruises, bleeding, corn-rows, swelling, and tap-outs as turn on's... but watch five minutes of a Maria Sharapova match and you're money.
I think CaptionRon said it better than I could, basically Tennis is a whole other ball game to combat sports. As I said earlier, sports involving grace and form are much more easily accepted and interesting in the mass public as women's sports. Blood and brute force, not so much. It just doesn't have any appeal. Frankly, for combat it looks weak as hell. The performance difference is far greater than sports like tennis / badminton / gymnastics etc. because of the greater importance of brute force, power and pure athleticism.
Women's boxing would be a better comparison, and just see how that's doing even after being around for decades.
Also I don't see Dana doing it as a cash out. Ronda is no bigger a star than the biggest women boxer, the casual fan would pay 10 times more for the worst "GSP beating up cans from the bush leagues" fight than they would for the biggest female mma fight in all of history. People just don't care, apart from a small niche fan base. It doesn't matter if Cyborg is pumped up with enough steroids to be a male horse, she would still get her ass whupped handily by mighty mouse and people had trouble getting interested for that flyweight title fight.
I see it more as Dana getting some, hence his sudden flip flop on Women's MMA. Right after him and Rousey being seen together alone at many red carpet events. You don't see Dana attending movie premieres alone with Jones now do you? Certainly haven't seen him sporting nude Anderson Silva T Shirts.
The profitability of this fight or the division don't matter to Dana, this is just dole for him. He's rich enough to afford a few indulgences.