Misunderstood.
Draco grew up in an environment where his parents (mainly his father) were constantly surrounded by bad people. They would talk about the Dark Lord, and what a great ruler he would be. About how he would improve the wizarding world, and make it a better place.
Draco, being a small, naive, child genuinely believed them. That Voldemort would indeed make it a better world for him to live in. His parents always gave him everything, and loved him with all their hearts; why wouldn’t he trust them?
But being surrounded by death eaters probably made his spoiled, and rotten attitude seem normal. He thought it was alright to put people in their place, and treat them however he wanted.
By the end of the series, he grew more mature and started to realize that these things were wrong all too late. He was done. Malfoy saved Harry’s life. He never wanted anyone to die on his accord.
So that’s Draco in a nutshell. He never knew any better. It’s just the way he was raised.
