The formula for X Factor is so transparent now as to be laughable. I do still get drawn in, but it has lost a lot of its shine for me.
I detest the tragic back stories. Absolutely loathe them. Adopted? Granny in a wheelchair? Childhood in care? Blind, deaf, one legged little brother? Where there ten of you crammed into a shoebox in the middle of the road sharing one cardigan between six for bedclothes? Great. You're in. 
I detest the sending home of great people only to bring them back in again, when it suddenly turns out that some other contestant is fired for some past scandal or misdemeanor that the production team claim to have had no former knowledge of, but conveniently for them it fills the papers for the next two weeks.
I maintain that they pretty much know even before the initial audition stage who they want to win, at least down to a top three, and they do everything they can to manoeuvre those people into pole position, pitting them against vastly inferior people who may give them a bit of a run for their money for a while, but not enough to rock the boat in the end.
I say 'before initial audition) because I firmly believe that most of the really good ones are not just random hopefuls who turned up on the bus with their sandwiches in a tupperware thing. They've been scouted, groomed, the researchers have been working closely with their stage school or whatever, for years and when they finally make it onto our screens it's because it's been by prior appointment, sometimes years in the making.
Often the people who get sent home early are sent home precisely because they are so good. They don't want anyone messing up their plan and getting more public votes than their ear-marked potential top three. It doesn't mean they aren't good - they just don't fit the brief for this year.
And the rest are just filler. A couple of useless people with novelty appeal, a few plucky underdogs, (I've been doing this for 25 years and you are my last chance) some people who have huge potential as rock musicians (I suspect this is compromising my artistic integrity but I'm prepared to give it a bash in the hope of some higher paying gigs for my band) but are totally wrong for the X Factor format, etc.
Sometimes they send someone home because in spite of being amazing, they just don't want another young, black female RnB singer (or boy band or whatever) because they've had two of those winners on the trot and they want to keep it fresh. And maybe Simon Cowell's record company is currently putting money and effort into another artist who is too similar. The fact that that person might turn out to be who the public like best is too risky so they ditch them before it can get out of hand.
They absolutely control it all from the beginning. We are idiots if we think we ever hold much sway in any of it. It has gone spectacularly wrong for them in the past, and their have been winners they never anticipated. So each series has become markedly more manipulated and controlled to avoid that happening again.