I agree with you on this, there were quite a few topics on the forum that asked to make the evil passage more reasonable, and less stupid, to give the player reason to think about joining the cult of the absolute. These are only early access issues, it seems to me.
I even assume that this was done on purpose, in order to study the opinion of the players on how they see the dark side of power and use it in their work. Larian could not say "we are studying the reaction of players to an evil passage, we will persuade them to play for evil" and make all evil choices poorly worked out by chance
They will absolutely have to change quite a lot about that plot because the "dark side" has to be tempting, that's the whole point.
And there has to be a whole lot of tempting in this case because they want you to
which is just a cartoonishly evil act. And
There has to be a SHITLOAD of incentive for me to do something like that.