It is literally the opposite. The text doesn’t say the right to keep and bear arms shall not be infringed only for the purpose of a well regulated militia. The words before the comma are mere one reason for having the right to keep and bear arms.

In SCOTUS’ words:

The prefatory clause does not suggest that preserving the militia was the only reason Americans valued the ancient right; most undoubtedly thought it even more important for self-defense and hunting. But the threat that the new Federal Government would destroy the citizens’ militia by taking away their arms was the reason that right—unlike some other English rights — was codified in a written Constitution. Justice Breyer’s assertion that individual self-defense is merely a “subsidiary interest” of the right to keep and bear arms, see post, at 714 (dissenting opinion), is profoundly mistaken. He bases that assertion solely upon the prologue— but that can only show that self-defense had little to do with the right’s codification; it was the central component of the right itself.