What makes Lelouch’s character so intriguing and so distinct from other genius protags is how he compartmentalizes his facades so perfectly that it has become his fatal flaw, and how it ends up driving the story.
Lelouch is a prince, a big brother, an ordinary student, Zero - he lives different lives that are equally important to him. And in his mind, he separates them so well he foolishly thought they could never overlap.
So when Shirley’s father died because of Zero, Lelouch was just in shock. He struggled to reconcile the two worlds in him. He never imagined it.
And he continued to not learn from it. Suzaku was unique in that he knows all of Lelouch’s facades sans Zero. Suzaku belonged in a unique position in Lelouch’s mind that someone as smart as him didn’t figure out Suzaku was at least related to the Lancelot. This is telling because even Suzaku have always had an inkling Lelouch was Zero. Lelouch didn’t ignore the signs; he was simply so blind to it because of how he divided his facades are.
And this part of Lelouch wasn’t something he chose to be. He didn’t wake up one day deciding to cut up himself in separate identities because it suited him. It was the consequence of his trauma being rejected brutally by a parental figure. This was his shield from a world full of discrimination and violence. Lelouch feared being rejected again, which is why he was always at peace around Suzaku, who knew him as a whole person, yet chooses to protect him. Suzaku rejecting Lelouch at the end of season 1 brought out wild anger and hurt and vulnerability; Suzaku, who was supposed to be the one person who would always be his ally and never hurt him - because both of them have shared their pains and joys honestly when they were children.
Genius protags aren’t supposed to be like robots. They are as human as anyone else.
Lelouch: Dandelions symbolize everything I want to be in life.
Suzaku: Fluffy and dead with a gust of wind?
Lelouch: Unapologetic. Hard to kill. Feral, filled with sunlight, bright, beautiful in a way that the conventional and controlling hate but cannot ever fully destroy. Stubborn. Happy. Bastardous. Friends with bees. Highly disapproving of lawns. Full of wishes that will be carried far after I die.
Shirley: *not looking up from her book* Edible.