Maybe canonically "Divine One" is actually just dumb, not evil. I can buy in not killing baby Damian by lawful good Lucian, even from pragmatic perspective it's a wise decision to turn on his side "Damned One", who is basically another Divine but from Lord of Chaos. And two divines are better than one. But killing Damian girlfriend and later after he turned to the dark side and started a war, sparing him and banishing Damian into Nemesis instead was so stupid.
Years after Lucian decided to genocide the elves, just to stop possible uprising from them and kill some black ringers, which in turn weakened barrier between Rivellon and the Void, and that led to the return of voidwokens... Everything is a started by Lucian, even situation in Divinity 2 is mostly is his fault.
So yeah, Lucian isn't evil, he just an idiot.
That would certainly explain it.
And also, "he's not the Divine, he's a very naughty boy."
