I'm fairly sure that Ramza had no idea that things would play out leaving Delitia king. The whole reason he got there is that no one thought it would end that way.

and he left a complete psychopath in control of the country.
I saw Ramza and Delitia as tragic hero figures, each in their own way. We all know about Ramza, but I don't see why having Delitia become king to help the country can't be a heroic act. I mean, overall Delitia probably killed less innocent people than Ramza did. (Think of all the people Ramza had to kill just because he was a heretic). Delitia was primarily stabbing people in the back who were already corrupt.

If Delitia was truly a tyrant than history would have recorded him as the king who came to power after the Lion War, not the hero who ended it.