For most of the modern Games' history, hosting was something cities competed hard for. Bids were contested by multiple serious candidates, campaigns ran for years, and losing was treated as a civic disappointment. That competition has thinned out to the point where the awarding process itself had to be redesigned around the shortage of willing candidates.
The explanation is not that cities stopped caring about prestige. It is that the financial structure of hosting became widely understood, and once a public that carries the downside understands the arrangement, the political calculation changes. The overruns that made the reputation were not a series of unlucky administrative failures. They are what this particular kind of project produces by design.
