That's a bit deceptive due to the large African American population in Alabama, which would obviously nearly unanimously back interracial marriage. In 2000, AL was 71% white, 26% black, 3% other. Meaning that in all likelihood, a majority of whites in Alabama voted to uphold the interracial marriage ban. Meanwhile, if you put the vote up in a nearly 100% white state such as Vermont or Maine, it would've passed with much more than 60%.
There's also the question of the veracity of that data to begin with. I highly doubt only 4% of people approved of interracial marriage in 1960.
So you're going to compare a racially polarized state with a fraught racial history (Alabama) to two very homogenous states that are far more liberal than the country as a whole and have/had fewer racial issues than the country as a whole (Maine, Vermont)?
Why do you highly doubt only 4 percent of people approved of interracial marriage in 1960? Were you alive in 1960?