This was in the context of British Rail having just wasted a huge amount of public money: https://en.wikipedia.org/wiki/History_of_rail_transport_in_G... . Beeching did the job he was hired for and did it well: he wrote a report that identified which lines were profitable and which weren't. The politicians who took action based on these facts are the ones who bear the responsibility for those actions.
To be fair his analysis would be better described as nearly competent than "done well". Government ministers were responsible for approving the cuts he recommended (and a few he didn't), but they did so based on partial and often completely inaccurate figures and without any challenge to closure as the only option. Alternatives like de-staffing and removal of common carrier obligations could have transformed the economic case for a lot of lines, as indeed could the faster roll-out of diesels.
