When one thinks of the Halloween franchise, there are usually two names that come to mind: Michael Myers and Laurie Strode. The ultimate survivor and killer duo of the slasher world, caught in a forever game of kill or be killed. Even though John Carpenter never envisioned a franchise when he made the first Halloween in 1978, the film has generated eight sequels and a short-lived reboot series, most of which follow Laurie as she continues her fight against Michael. The films, except for Season of the Witch, focuses on serial killer Michael Myers, aka the Shape, who was committed to a sanitarium as a child for murdering his sister, Judith Myers. Fifteen years later on Halloween night, he escapes to stalk and kill the residents of his hometown.
One of his intended victims was Laurie Strode, who becomes the sole survivor of his killing spree. Actively stalking her around town then later calling her on the phone, same as how any serial killer would show interest in their next target. However, there is never any explanation given for Michael's obsession with Laurie. He's just portrayed as an evil being with an itch to slaughter. Fortunately, a new Reddit theory attempts to tackle the question by posing the idea that Michael didn't actually care about Laurie.
Myers' motives changed when Carpenter was forced to write the sequel in 1980. He did his best at creating a reason for why Michael would bother chasing Laurie down a second time in Halloween II, coming up with the idea of them being siblings. This later became cemented in the film's foundation, even though many seem to forget that there never was supposed to be any sequel in the first place. Meaning, they weren't ever supposed to be related, and Michael's motives were meant to remain a mystery.
As the theory states, Michael Myers seemingly doesn't care about Laurie Strode. With the release of the 2018 sequel that dismisses the sibling detail, a new timeline is created where Laurie is once again just another target. In the film, Michael returns to Haddonfield to continue his killing spree, and it's not until after he actually sees Laurie alive that he goes after her again. It's the other characters in the film that make the claim of Laurie's importance on account of her being the sole survivor. If anything, Laurie symbolizes our need to constantly rationalize tragedy.
It's clear that Michael was interested in Laurie when he first saw her in 1978, seeing as he didn't stalk Linda, Annie, Bob or Paul, the other people he killed in that film. He was coming to kill Laurie because, for him, stabbing is the equivalent of a Valentine. There's still the possibility that being a pretty blonde, she reminded him of his sister Judith. However, this still promotes the idea of him wanting to kill Laurie because he was attracted to her as he killed his sister only after seeing her half-naked fooling around with her boyfriend. If Laurie hadn't been there, though, he would have just gone after someone else.
Nothing about Michael's behavior indicates that he is motivated by revenge or anything other than a need to keep on killing, which gives this theory some actual credibility. Michael Myers is just a cold-blooded killer with no motive, making him much scarier as a horror icon. Billy Loomis from Scream said it best, "it's a lot scarier when there's no motive."