I suspect the real reason is "maybe turning profit-skimming by intermediate layers of management into an art-form, makes any large-scale project-costs trend to

I suspect the real reason is "maybe turning profit-skimming by intermediate layers of management into an art-form, makes any large-scale project-costs trend to infinity". HS2 spent ungodly sums on "consulting" and management fees to do stuff that, back in the day, would have probably been carried out by a couple of commandeered civil servants. But I'm sure all their Word reports have nice headings and lots of "holistic" something.