Shouldn't the plaintiff though be the one to take on that risk?
If the damage of losing market share is truly irreparable, then the court would be doing irreparable harm to Samsung on the basis of Apple's unproven allegations.
As I understand it, a court ruling like this is based on an initial assessment by the Judge that Apple is likely to win, as the patent(s) are currently valid and it appears (to the Judge) that Samsung is violating them.
If the damage of losing market share is truly irreparable, then the court would be doing irreparable harm to Samsung on the basis of Apple's unproven allegations.