A lot of things will cause deer to move to different areas. As has been pointed out, and a major reason for deer moving out of one area into another is a change in available food. I've seen this often, one year there will be lots of good sized acorns in one area and the deer are plentiful, another year the acorns there are scarce, and the deer likewise.
Weather can change deer patterns, especially colder weather, they'll move the shady side of an area to an area that catches more sunlight in winter, more so on colder days, then when it warms up, poof they disappear again.
Also, as pointed out, the rut will spit up bachelor groups of bucks, they'll become more solitary, and establish territories, although more than one buck may use a scrape line, but often their scrape lines overlap, and that's where you'll find bucks locked in combat. Bachelor groups of bucks tend to hang out in low areas that have lots of grass and water in the summer, then they'll head to hilly areas that have secluded flats to establish their scrape lines.
Hunting pressure will move them to, not always that far, usually a mile or so, depending on the pressure, available food/water, and shelter from weather. You might find them in area one day, then weather changes and they move to a better area.
Deer are very predictable, it's just that the things that cause them to change their patterns are very random.