I mean on one hand midterms don't really correlate that well Snyder won by 20 and then Romney lost by 10.
That's... nonsense?
In 2010 Snyder won 1,9M votes, the most a House Republican has ever won before or since.
(Conversely, the Dem has garnered 2.1M twice, in 2006 and 2018.)
This correlates perfectly with Bush getting 2M then 2.3M, McCain getting 2M, Romney 2.2M and Trump 2.3M
The pattern is clear: Democratic enthusiasm is the only real issue in Michigan, as the GOP has a hard ceiling of about 2.4M votes.