It should go without saying, but the Okahoma City bombing wasn't a mass shooting, which is what is being discussed.
And what's your point about traffic deaths? By that logic, heart disease killed more people over that interval, should we stop caring about traffic deaths?
Well, generically the topic is domestic terrorism.
I know that I'm verging on whataboutism. But there is the tendency to amplify outrage based on public sympathies.
I worry lots more about official government violence. Consider deaths of US troops in Iraq during the mid 00s. About 800-900 per year.[0] Or far worse, deaths of Iraqis, which exceeded 20K per year during that period.[1] The same issues that are driving mass shootings will likely result in another major war. That's the thing to worry about.