I know this thread is 8 months old but I came across it as I was trying to find some miracle method to revive my iPhone X. My X is right at 2 months old and died in it's sleep last night for no apparent reason. I've tried the hard reset, I've tried the iTunes thing. Even Verizon tried to bring it to life. Nothing. A replacement phone is being overnighted to me, just sad to see this is apparently not as rare of an issue as I thought it might have been. My Android friends are enjoying my grief.
Not every device will be perfect and anything can be experienced with an electronic device, as things can go awry. Granted, most iPhones will perform without issue, perhaps you just received that _one_ phone that had a hardware fault that was out of your control.