I've been to Exeter several times cos a friends used to live there, and it is pitchfork country (btw, I don't live in London any more, so this is also from a provincial perspective).
Also you are disproving your own point, not proving it, by acknowledging that even those people from the ends of the earth still wanted to vote Labour despite their dislike of Corbyn, so personal dislike is only a single factor and actually not even that important compared to tribalism and policy. Further point is that none of those who were criticising him would have run on that policy platform, so it kinda doesn't matter anyways - and the media would have torn apart anyone proposing an alternative to the ongoing neoliberal consensus (although as recorded far and wide, what Corbyn was proposing was not actually that radical at all, showing how far right the 'centre' has travelled).
Central point being that your notion of a leader with domestic policies similar to Corbyn's not being equally disliked by Exeterians, is a fantasy. They would have hated his equivalents equally - the problem that many people had with Corbyn in 2017 was not the things he's actually done wrong, but that his policies were seen as suspiciously left-wing.
Anyways, look at the link I sent you, and it will show you that you're wrong on this. Corbyn was nowhere near as unpopular as he is now, and in fact was wildly popular among certain constituencies. And he outperformed the centrists of 2015. Even many rightwingers would acknowledge in private that he (and the structures supporting him) played a blinder in that election, totally rearranging the idea that trad left-wing/left-centrist policies are unelectable.
Also, just as a point of interest, did the people you talked to say why they didn't like Corbyn? Suspicion of course is that the personality issue is a cover for the fact that, hey, his policies just don't fit with what those people want. That they only had a Labour MP in 97 tells a similar story.