For the ones with the best intentions they probably think that, on average if not in every particular case, they're pulling the switch to make the trolley hit o

For the ones with the best intentions they probably think that, on average if not in every particular case, they're pulling the switch to make the trolley hit one person instead of five (so to speak), and that not doing so would make the world a worse place. For the ones with the worst intentions, it's likely something to do with chasing material and/or social rewards. (edit) And they don't much care about how much it hurts others.