It seems that there was actually somewhat of a swap between people who INITIALLY supported Trump in the primaries and those who most loyally support him now. Obviously, there were legions of Trump primary voters who continue to support him now, but he did not win a lot of the people who posters stereotype as his core supporters, and he won a lot of self-described moderates and Republicans from areas that wouldn't "stereotypically" be drawn to him in some people's eyes.
Yeah, in the primaries, Trump did decently with Southern Evangelicals but not very well with Midwestern ones. It was the Northeast that was Trump's strongest region in the primaries, and this was off the backs of moderate and Catholic voters; Trump also did surprisingly well with more affluent, educated voters in Massachusetts in the primary there, for example.
I don't think it was so much a "swap" though: I think people who voted for Trump in the 2016 primary are still quite loyal to him; it's just that between the primary and the general election, there was a big, still-enduring increase in non-Southern Evangelical support for Trump - for example, Trump did very poorly in Northwest Iowa in the primaries but ended up outperforming Romney there in the general election. The reason we don't see those Northeastern voters as 'typical' Trump voters is because so many fewer people voted in the Northeastern GOP primaries as opposed to the Democratic ones, so they are fairly small in number to other groups even if they are pretty strongly pro-Trump.
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