Bad engineering is suspected.
Deaths on collapsed Rio de Janeiro bike path deal safety blow to Olympic host | World news | The Guardian

Either a bad sign of their engineering skills or building skills... either way, a bad sign.

Or the old problem of cost / schedule / quality : pick 2.

scott s.
.

Let us remember those that died.

Good point, and also likely to have occurred elsewhere in their Olympic rush to complete other things such as venues, or sewer treatment plants...