Thatcher knew that mining and manufacturing were the strongholds of the union movement and that, to destroy the strength of the unions, she had to destroy that stronghold.

Rubbish! Mining was in decline for decades as has been pointed out innumerable times on here and manufacturing was increasing.
Producing far more valuable widgets with less people.(The only metric the economy is interested in


https://ourworldindata.org/death-uk-coal


https://www.theregister.co.uk/2010/02/22/manufacturing_figures/

Coal production had been in decline since around 1914, Manufacturing has gone from strength to strength post WW2
Awkward things facts. This is why certain remainiaccs never produce links. Links are can substantiate facts. Whimsy and opinion count for nowt.

Of course the magnificent Thatcher showed the unions that governments run countries, not jumped up upstarts like the scallywag Scargill.