I believe that when someone makes the decision & takes the ultimate action to end their life, it is a confluence of discouraging/triggering events and long-held hopeless thoughts.
Sometimes, the opportunity is orchestrated or purely happenstance.
Sometimes, there is a trigger that is only known by the suicidal person.
Sometimes, there's nothing anyone (who knows & loves the suicidal person) can do, when that confluence of discouraging events and hopeless thoughts converge.
The person may have been waiting, for some time, for that perceived convergence as a sign to end their life, and when they believe the sign has appeared, they are relieved to know that their suffering will soon come to an end.
This is one of the things suicidal people struggle with day to day - looking for the "sign" that 'now is the time'.
This is one of the reasons it's so difficult to determine who might take their lives by suicide.