Why are Republicans so much stronger/Democrats weaker at the state level?

[Indy Texas]

1. Most governors run in off-year elections with lower turnout.

2. There are fewer restrictions of campaign finance at the state level than at the federal level, making it easier for outside groups to flood races with money.

3. The current districts were drawn very favorably to Republicans in most states due to them controlling the redistricting process in most states following the 2010 elections.

[Indy Texas]

2010. It also gave them the chance to draw very favourable maps for the next 10 years.

This is pretty much the answer, but I think republicans overall are trusted a little better at the local level.

I think it's more that people who self-identify as Republicans are more "loyal" to their party than people who self-identify as Democrats.

There are Republicans in places like Vermont and New York who will dutifully tick off all the R boxes up and down the ticket even if they quietly murmur that some of them may be a tad too conservative. There are so-called "Democrats" in Oklahoma and Kentucky who will vote in primaries like clockwork but refuse to vote for any Democrats at any level in general elections because they "lost their way" or "ain't the party of the workin' man no more."