Survival of the fittest employers. Those that ran at a profit, unlike the mining, car and steel industry. Strangely enough employers that cannot run at a profit go bust, unless government continuously subsidizes them. This is why Beeching sorted out the railways, Macgregor the steel industry and coal had been declining for decades before Thatcher arrived. In fact the ex labour mp Robens presided over a large part of the coal industry death throes long before Maggie came on the scene.
It is also conveniently overlooked that similar declines, for steel, also occurred in the Rhur Valley and Ohio. Was Maggie Thatcher responsible for that too?
So nothing to do with spivs at all. It is all in your mind.