1. The team does not communicate sufficient details on project status and issues.
2. Stakeholders do not pay sufficient attention to project status and issues (or the lack thereof).
This does not mean that a communicative team and responsive stakeholders guarantee success. There are too many other things that can go wrong. But it does buy you time to identify and correct for issues before they become catastrophic. In the worst case, stakeholders can determine that things are going from bad to worse and can chose to cut their loses by abending the project.
Ultimately, a combination of clear team communication and healthy attention from stakeholders is your best hedge against sudden and costly project failure.