Actually, Bevin was quite good. He wasn't reelected because he ticked of the teachers by trying to fix our very, very badly broken pension system.
How broken? I saw an article the other day that California is in debt many billions of dollars, which puts it in 5th place as far as the most debt. The only states deeper in depth are: Illinois, Massachusetts, Louisiana?, and Kentucky. So, Kentucky is deeper in debt than California but has only a fraction of the economic output, so the outlook is much more dire. Bevin tried to get started with a fix, but the teachers would have no part of it.
Look at the voting: Trump won Kentucky by about 62-38. I saw an article about the Kentucky voting where Bevin lost. That year there were 30,000? fewer votes cast than in the previous gubernatorial race. Bevin lost by 4,000 votes. So, it looks like thousands wouldn't actually vote for Bashear instead of Bevin, they just didn't vote at all which allowed Bashear to win.
He lost for a number of reasons - saying really stupid things like teachers rallying in Frankfort were causing child molestation really damaged him. His final nail in the coffin was a week before the election coming out for tolls in Northern Kentucky, causing him to lose a lot of support in that Republican stronghold - more than enough to make up the margin of loss.