Some context might be of interest here. The chimneys that Dibnah worked to demolish were usually attached to cotton mills in and around Manchester in North Wes

Some context might be of interest here. The chimneys that Dibnah worked to demolish were usually attached to cotton mills in and around Manchester in North West England. The cotton industry was in steep decline there in the 1970s and 1980s and one by one these mills became unprofitable and closed down. Even if the mill building could be repurposed the chimney wasn’t needed and would be expensive to maintain. I suspect Dibnah got the work because he was the cheapest and the mill owner would typically be very short of cash.