alt Hacker News> Vogal was a boondoggle but it didn’t get construction approval until 2012 and like many projects ran into COVID delays on top of everything else.
Well there you are, then: projects experience delays in construction approval and run into other unexpected delays, which extends a ~10yr estimate.
The 10 year estimate comes from a range of projects including some that go very badly and others that didn't.
You can always pick worse numbers by using a smaller sample of projects, but it isn’t necessarily meaningful to do so. California’s high speed rail has gone far worse than Italy’s projects, America is currently comically bad at large construction projects.