Understanding can sometimes come quite quickly. You read a line of text and the next thing you know, you know. It can, though, take a bit of digging to figure out what the heck was going on.
Draco did not like having to figure things out. He was a take charge, give it to me straight kind of man. After all, when the enemy is coming knocking at your door, you want to be ready so you can hide.
Lucius Malfoy, on the other hand, loved to confound everyone. Just take a look at the last line of his will:
Draco will keep my Wednesday 4:30 appointment.
No explanation of what that appointment was. Where it was. Or why it was to be kept. Just an arrogant demand that was expected to be obeyed. Draco would of course, obey. He was, after all, the perfect pureblood heir.