The NHS used to have a General Management Training Scheme (which rejected me twice!) that was ostensibly about training 'administrators' to become 'managers' but was in fact more about grooming the next generation of upper & senior NHS Leaders through training, education and mentoring.
Ant some point - possibly mid/late 90s this fizzled out with the notion that senior managers were best recruited from industry (and the armed forces in some cases).
Then as you say, management consultancy firms got the ear of the Trust Boards and that's where we are today - in a revolving door where all exits lead to a different sort of mess.