Striped skunks defend themselves chemically, and most mammalian predators learn to avoid them. Great horned owls do not. Skunks appear regularly in their prey remains, and researchers handling wild-caught birds commonly report the smell on the plumage.
The usual explanation is olfactory: birds generally have limited olfaction, and an owl hunting by sight and sound in near darkness is not deterred by an odour it barely registers. The spray can still irritate the eyes, so the defence is not entirely useless, but it is far less effective against an aerial ambush from behind.
The ear tufts, meanwhile, are not ears and have nothing to do with hearing. They are feather tufts, and the leading interpretations involve camouflage, breaking up the head outline against branches, and visual signalling to other owls. The real ear openings are hidden at the sides of the facial disc.