I don't understand how statewide races can ever end up without a serious nominee. What, the state party can't convince some random state rep to give it a go? Even as a sacrificial lamb?
Campaigns are expensive and one consuming. Not everyone can just stop their lives for six months on something they know is pointless.
Which is often why when you do get a rando state legislator, it's cause they lost out locally. Redistricting, coalition shifts, or factional infighting renders their chances of reelection low, which raises the comparative value of a long-shot statewide campaign.