If you don't have an organization that can break it down to a smaller projects then there is a question if doing it as one large project has a higher or lower chance of failure.

Shouldn't that depend upon complexity of change but who cares. CIO have a short tenure so collecting the bonuses and leaving before house of card collapses works.

It's all about managing the personal bonus and career, who cares for the success 9f project?

It depends on complexity, but I think it's more of a situation akin to refactoring or rewriting a complex code base. A total rewrite is always an attractive thought, but a real focus on continuous refactoring in smaller portion at a time is often lower risk, lower cost, and faster in the end - and I suspect it's the same with large bureaucratic processes too. It's also a way to sharpen the skills of the organization in small steps with lower risks for failure (and improving future project steps...).