In the 2018 film, we learn that for the past 40 years, Michael has been detained and living in Smith’s Grove Sanitarium. However, during a prison transfer, Michael crashes the bus and escapes on the night before Halloween. We all know what that means. He goes on another killing spree, and once again, Laurie goes head to head with him. She survives, and unfortunately, so does he.

Source: https://www.distractify.com/p/how-is-michael-myers-still-alive-halloween-ends