Say a DUI driver kills a random family of 5. Is that going to make national headlines? Probably not. Very little to be gained politically. It doesn't really enrage us because we love and celebrate alcohol too much to be capable of villainizing it like guns. So as a result, it doesn't spread very far on social media.
Now say a raging incel shoots 5 people at a mall (2 die, 3 are injured). Is that going to make national headlines? You bet. It easily enrages at least half of us since guns are a wedge issue. Hence, it spreads like wildfire on social media. As it's spreading, it is further coupled to politics whenever people use the story to further political goals like mobilizing peers to go out and protest, drum up support for a preferred candidate, and more.
You won't see a public reaction to car accidents similar to guns until the media decides either alcohol or cars are villains that need to be eradicated from society.