Why did the masked man wanted to kill her?

There were markings on his crossbow to indicate how many people he had killed. He was a serial killer.

like many real life serial killers their motive doesn't make rational sense. This guy implied that he got a kick out of toying with his victims. He wanted her to psychologically suffer before he would enter the house to kill her. For him it was fun, a cat toying with a mouse. The motive was power and sadistic pleasure, sadly real motives for real messed up humans.

Because she was home.

The movie isn't stupid, you're stupid because you didn't understand it. He killed people for fun.

CG gore is the worst thing that has ever happened to the horror genre.

As many have said, he was a serial killer, he found what he thought was an easy target to have fun with, there were multiple number markings on the crossbow to show how many victims he's claimed (show, don't tell; horror films have been forgetting that the most). You know a lot of people kill for the fun of it, so it being motiveless really isn't stupid. And the film showed you that he was a serial killer, unless you weren't paying attention, it was kind of hard to miss the crossbow marks.

Killers don't always have or need a motive to kill. They do it for their own sick amusement. People who just kill indiscriminately like this are called serial killers. That's what he was. Obviously that went over your head.

Respect what you have 🌌

Clearly got off on killing terrified people. Which is why he said he was going to wait until she wanted to die before he was coming in to kill her. He was very obviously a sociopath. People like this actually exist.

There is a motive--he is hunting her like an animal, and clearly enjoyed doing so. What else do you want?