I think the most astute observation is that Sturgeon failed at the thing that she was most confident in - that she was a superior politician.
"Like vampires who attempt to blend in undetectably with regular humans, successful politicians must understand the public mood, if only to mimic or manipulate it. Neither group can afford to slip out of touch with the real-life concerns of normal people. The lifeblood of politics is connection, feigned or sincere. You have to understand, or pretend to, the hopes and fears animating the populace you’re supposed to be serving."
That is precisely what happened to Sturgeon. One doubts her commitment to the trans cause - instead she'd made a catastrophic miscalculation and her greatest asset, her self-absurdness, turned to hubris and became here nemesis.