Is this coincidental, strategic, or simply vindictive? The former is quite hard to believe. Either of the other two possibilities are grotesque.
It's obviously strategic / ideological. These are seats that the Tories had no hope of winning, that they have no connection to, effectively no visibility of, and don't generate much money - why do they care what happens there? It may as well be another country. They can instead bung support to their strongholds and marginals to keep themselves in power. Hell, the Tories killed a lot of these towns in the first place when they decided the UK should be a nation of bankers and there wasn't any point making anything any more. Manufacturing was always going to decline to some degree, but Thatcher didn't just let it decline, she loaded the economy against it, blew it up, and let the communities that had depended on it rot. There was political gain there too: permanently weaken Labour's base by impoverishing and breaking its communities. Ever since the one-nation Tories slipped from ascendency, the party as thrived on division for years: the poor are lazy, feckless, useless, crime-ridden and deserve what they get. They're there to be feared, denigrated and controlled not helped, and as long as they can keep the middle classes believing that, law and order and reduced welfare wins the Tories their votes.
Now of course having exploited misery, nationalism, anti-immigration and Brexit to break Labour's grip on many of these places, they may actually pay attention so they can try to keep them. Oh, the irony.
That said, I don't think they will. It's hard to get government support past the ideologically laissez-faire ultras that constitute the cabinet. One look at all the answers to how to make the UK succeed post-Brexit, and they're all deregulation, lower taxes and reduced public services, etc. - that's why Brexit and libetarians have gone hand in hand. A decade of misrule has left the country up to its eyeballs in debt, with covid-19 the cherry on the top and Brexit to come, so money to fix anything is scarce. And even then, the colossal problem of how they keep these towns alive given it's a global phenomenon that developed economies increasingly revolve around large cities no-one has yet had an answer to. (In this sense, potentially the answer is to strengthen regional cities and it will drag surrounding towns up - areas with no cities like Cumbria or Cornwall are just irrevocably stuffed.)
The left tends to care about people. Those who run the Tory party generally don't - they're interested in more abstract notions like national greatness as measured by GDP, global influence, winning wars, etc. If they can build those on a bonfire of the plebs, they'll be stocking up the firewood and petrol.
