Well, depends on what you mean. Compulsive hoarding is a mental disorder characterized by behaviors that are both deeply irrational and obviously detrimental to the sufferer (in terms of their ability to manage sanitary conditions at home, manage personal finances, or otherwise function in the society).

Prepping, in contrast, is a behavior that can be explained rationally (even if there may be some disagreement about whether it's the best allocation of one's time and money) and is not supposed to have any debilitating effects on your quality of life.

Of course, the lines are blurry. The term "hoarder" is sometimes derisively applied to people who are disorganized or have more stuff than others, without clearly crossing into the territory of self-destructive behaviors. And there are some preppers who start with a rational train of thought, but go to such extremes that it's difficult to argue that they still have their stuff together. That said, the "crazy prepper" trope is more of a Hollywood invention than reality.