Draco Malfoy wasn't a humble man, not at all. For all his life he was taught, that he was better than everyone else just because of his family wealth and pure blood status. There was no one to tell him otherwise, so he believed it without questions or doubt. And at the time he actually met someone who disagreed with this "pure blood shit" it was too late for him to change his way of thinking. As if he had any intentions to do so.
But now, for the first time in his life since Dumbledore's death he wanted to do something right. So when his Lord asked the students of Hogwarts to join him, instead of a proud stepping forward he hesitated. Was this really what he wanted? Was the death of his classmates and teachers what he was wishing for?
While watching his classmates and teachers fighting for what they believed was truth he had his own time to think. They were braver, more honest and everything he and other Death eaters weren't. Yet he was taught he was superior to them – to mudbloods, blood traitor and muggles. But how can he deny what he saw and experienced on his own? How can he still believe he was superior to them?
So he wanted to say – "I am not going to follow you anymore! I am not going to live in fear of you!" For once he wanted to stand on the right side. For once he wanted to do the right thing. Now, for real.
But deep in his heart he was still the same coward he was for all his life. So when his mother asked him, he followed. He stepped forward, but instead of telling what he wished to say, he did the easier thing – he took his mothers hand and followed her home.
Because his family was the only thing that was making a sense now. His family was the only thing he could depend on. He left his hesitation back there on the destroyed ground of Hogwarts and moved on.
For the second time he wanted to make things right. For second time he failed.