Ronda really didn't "decide" to strike, it was the only real way she had to close distance. Miesha can shoot, Ronda can't and or doesn't. I assume can't because of her knees.
But yes, as I've said before, the Holm fight was closer than it appeared at the time, at least in the first round. Ronda did get her to the ground at one point and just as easily could have walked away with a sub, but didn't. Rousey's ground game isn't about control, though, and I think to tap out Holm you need to be slow like that and work on position because she's really athletic and can scramble well. I'm not sure Rousey has the patience to take the back, although I do think she has the patience and skills to get full mount. GNP seems more likely to me than sub.