Yes, but that reliability is not the one that we normally think of when we use the regular language word 'trust'.
'I trust the pilot' does not imply that I think that the pilot will have a long and healthy life. There are two pilots because one might have a medical emergency, emphatically not because one might go mad.
In fact, if one does go mad, even with the other one present, there are plenty of ways in which the 'mad' one can run the plane into the ground if they so choose to.
So the 'two pilots in the cockpit' kind of redundancy is to protect against the cases of individual pilots becoming incapacitated.
Of course having another pilot in the cockpit will probably somewhat reduce the chances of a pilot with a mental issue being able to inflict damage simply because he'd have to either get physical with the other pilot or at a minimum would have to look them in the eye. But that's nowhere near what is required to stop a plane from crashing if one of the pilots decides to do it.
Which is one reason why it doesn't really matter if a flight attendant is present in the cockpit instead of another pilot. That's mostly a psychological issue, not a practical one.