I recall that once upon a time, Sturgeon said an indy ref would be a once in a generation thing. She lied. She changed her mind.
I also recall Sturgeon beating May aboot the heid cos May "did not have a mandate to govern".
So it strikes me that of all the people on the planet, Sturgeon should have been best placed to recognise that May, like herself, was a politician and thus highly likely to change her mind, especially when Sturgeon was asking herself for another election..
Lying and wrong-footing the opposition is second-nature to politicians. Sturgeon utterly, naively miscalculated and should have known better.