Hard to say, but I can at least speak to contributions from a lack of government expertise mixed with private corruption. I've seen this in my own local government.

Generally no one employed by the city knows how to look at an expense report from a construction job and check it for plausibility; this allows some outrageous pricing for things like a few tons of bricks. Sometimes they'll hire a consultant to check the books, but often that consultant is chummy with the contractor.

In other countries where government is trusted a bit more, it's much more normal to have an engineer and a construction project manager on staff to look at a report and tell you you're getting bilked.