MN is anchored by a larger metro area than WI and IA, whereas MI had more non-college educated voters.
Trump did better among the college graduates demographic than among those with high school or less in Michigan, so not sure what you're talking about.
The question was, "Why did MN stay blue when the other two flipped". MN has more college educated voters, who swung to Hillary, therefore preventing the state from flipping. Got nothing to do with the fact Trump did better with that group in MI than he did non college voters.