“Nationalisation” has always been a political act driven primarily by ideology. It is significantly different from situations where Government supports a failing business. Here ideology plays little or no part. Effectively Government temporarily provides access to funds (etc.) to help the business survive when conventional lenders (mainly Banks) are reluctant to do so.

The drivers of Government support do, of course, include political considerations. Closing a plant or a company that is a significant employer puts people out of work, increases the quantum of unemployment benefit payments and is socially disruptive. But the hard reality is that for a business to survive and prosper it needs more that temporary funding.
Steelmaking over the past few decades has moved to countries which offer competitive labour costs, economic access to raw materials and scale. China produces well over 50% of the world’s Steel. Other nations have roles to play but the main opportunity is added value production. British Steel’s production is negligible in global terms. Others do, or can do, better and (especially) cheaper.
There may be a social case to support British Steel, but there is no case to “nationalise”. The harsh reality is that we do not need subsidised steel production.