Not over night, not in 4 years, but just as they died, they can rise from the ashes, slowly.At the convention stage of an election both Trump and Biden will be focused on winning the election.
IMO the selection of Vance and rhetoric about rebuilding small towns is primarily to put the electoral votes of Pennsylvania, Ohio, Michian, Wisconsin, and maybe Minnesota in the Trump win column.
Does anyone really believe Trump or anyone else can somehow alter the factors which have the economic demise of the rust belt small towns? Heck, I read a book predicting this some sixty years ago and it happened. Gradually but surely.
Of course it is a Herculean feat with half of the country (cough rinodems cough) working to make it not happen.