If you trust them, let them fail.
If you trust someone enough to do a job, let him fail. The hope of course, is that he will succeed. But he will have to find a way to succeed on his own, through his own process.
After all, if you didn't trust him, then he shouldn't have the job in the first place.
Hope is not a strategy for success, and it shouldn't replace trust. In other words, you can hope someone succeeds if you trust him. But you can't simply hope someone succeeds.
The other side of this coin is that if you don't trust someone, don't give him the opportunity to fail. Because it will affect you. If he fails, and you gave him the opportunity, you fail.