The history is longer and more tangled than that.

1951 - Nationalised by Attlee (Labour)

1953 - Re-privatised by Churchill (Conservative)

1967 - Nationalised again by Wilson (Labour)

1988 - Privatised again by Thatcher (Conservative)

1999 - Allowed to merge with Dutch Hoogovens into Corus by Blair (Labour)

2007 - Allowed to be sold to Tata Steel by Blair (Labour)

2016 - Tata allowed to sell to Greybull Capital by Cameron (Conservative)

2020 - Takeover by Chinese Jingye under Johnson (Conservative)

I worked there for three years in the mid 90s.

Personally, I think it should have been left alone after 1951.

But it is arguable whether ideologically driven militant unions would have destroyed it in the 1970s and 1980s.