I think you have to remember what both Labour *and* the middle-of-the-road Conservatives had managed to do to this country up until 1979 to see why Mrs Thatcher did what she did.
Only five years earlier, in 1974, the National Union of Mineworkers effectively forced out Ted Heath's elected government.
British Leyland were almost perpetually on strike for one reason or another; it was a wonder they produced any cars at all, they were so busy destroying themselves.
"Managed decline" was the phrase that the civil service used at the time. Our GDP had been overtaken by that of East Germany (*), and really all we could hope for was to gracefully crumble into ruin and irrelevance.
Of course there is much to criticise in what happened after 1979. Perhaps the biggest mistake was the doctrinal adherence to using money supply figures to determine interest rates, driving them far too high, with the consequences that TJ and others have alluded to.
Now, where did I put that flame proof suit?
(*) Of course, they were faking the figures.