I think you’re overestimating non-league crowds! Half the teams in the conference currently aren’t even averaging 2k, Worthing & Lewes play 2 levels below that, Hastings even further down than that.
I am not overestimating non league crowds up North. Reason they are low is because so many clubs close to each other so are competing for supporters. (Accrington 8 miles from Burnley eg )It is not the same down here especially when Brighton are away. Our senior sides all have a big catchment area to attract supporters with little competition