Most of the money is not being spent on things that advance the project. The people most involved don't want it ever to be finished; that is when the money stops.
None of the money is wasted, as such; every penny goes into a pocket.
Things like it happen here and there. It took very long to build that Finnish nuke, which might be an example. It depends on the political conditions: typically, to get a big pot of money together needs support from a broad swath of supporters, who then each expect patronage, a piece of the pie. As long as the money is flowing, everybody involved stays happy, regardless of how much actual work is getting done.
Even in the US, not all public-works projects are afflicted. Solar and wind power systems seem mostly not afflicted.
When it seems like the money might stop flowing, there is some motivation to actually deliver a result, if just to save face or avoid prosecution for fraud. Even if not, indictments are rare, and in any case none of the money is ever returned.
