If I could have done something to prevent it, but chose not to, and someone died, I would feel just as bad as if I pulled the lever and killed someone.

I can’t say what is objectively true, but I can say that if I were in that situation, I absolutely would feel responsible for the outcome if I could have reasonably affected it.

Look at it selfishly:

• 100% chance of killing someone
• 25% chance of killing someone

Pulling the level is the only way to have a shot at not being saddled with the guilt of killing someone. Sure, killing 5 people is worse than killing 1, but avoiding that personal impact entirely is a desirable goal in and of itself.