She is getting out now, as she can disavow involvement in the nastiness of Kavanaugh (hoax?!), can walk away from the job with Trump (and Republicans) touting foreign policy success, and get out of the job before the seemingly inevitable (where have I read that before?!) November election debacle.
As you rightly state, she is now seen as a Stateswoman, and gets to write her own next chapter, as she readies herself for what comes next politically.
She is, by far, the most appealing Republican candidate for the future...of either sex.
Governors are very electable, because they have...governed! In addition, she is not known as being extreme, and is very appealing to women.
How ironic would it be if Republicans succeeded in electing the first female President, who has Native American roots?!