Yes the second and third decades of nuclear weapons testing were definitely more destructive then the following. The Partial Nuclear Test Ban Treaty of 1963 definitely helped slowing down the destruction by a lot. However e.g. France—a non signatory—continued detonating their nuclear bombs above ground on and around their pacific island territories well into the 70s. The environmental damage (and damage to the nearby human communities) is still very much present today.

But the fact that the PTBT was signed by most nuclear states which slowed down this pointless destruction—and later the CTBT, which almost stopped it in 1997—shows that even humans with our demonstrable aggressiveness do work to limit our destruction when said destruction doesn’t contribute to the enrichment of a subset of other members of the species.