The North is simply experiencing its first wave with a vulnerable population that was largely unexposed earlier. When we went into full lockdown, West Yorkshire had very low levels of infection. My ward had zero cases in fact. Most of Calderdale was the same. When things re-opened after the summer and schools/colleges returned, that large vulnerable population became exposed ... largely for the first time. It will peak in the north as it did in the south.
The other stuff holds true though that we have large areas of deprivation in the north, and in the West Yorkshire region, large BAME communities with high rates of underlying health conditions. I've been working with a group in Bradford who are trying to encourage the pakistani community to embrace the outdoors and hiking more. They were telling me about the sedentary lifestyle and high carb diet ... and how it has huge impact upon health in their community, particularly amongst the women.