As I mentioned in my other comment, the gun related deaths halved 2 years after the gun laws [1]. Furthermore, in 1996, the gun deaths per capita were 2.84, the homicides were ~650 per capita. So of course you will barely see a difference with the homicide graph. The real difference is that there have been no mass shootings for 20 years.

So yes, it really is that simple and completely obvious.

[1] https://www.gunpolicy.org/firearms/compareyears/10/rate_of_a...