That's actually a bit simplistic Trisher, it wasnt just about Brexit in the North. Something to do with ambition as well and a view that the labour party was irrelevant to the North. Perhaps assumptions about the working class they claim to represent. The union issue for example, I work in a sector mainly staffed by poorly paid women, not one is in a union, discussion of trade union legislation would have no relevance for them whatsoever.
Starmer comes from a working class background not that I care one way or the other about that. Corbyns early life was not one of deprivation. Again none of this is relevant, this kind of identity politics is not good for the labour party.