Media coverage. Both as purely popularizing it, as well as making us more aware of them. Gun violence is down, look at FBI stats over time, awareness of gun crime is up. We know several shooters have gone that direction just to get attention. It would be better for the media to drop the coverage on the shooter themself. The people with messed up minds see the attention and want a piece of it.
Lack of understanding of guns. People werent taught how to properly respect/handle weapons, so the disconnect has made using them violently against people more likely. When you are taught how to use guns, safety, both you and for others, is hammered into your head. We removed "drivers ed" from the circulum and get shocked when the related safety measures fall apart. This also goes to safely storing/maintaining weapons as well. It's a learn as you go culture now, instead of being prepped. Now instead of commonly seeing guns handled properly most of society only sees guns being used in games or movies against people.
Kinda relating to the above but the impression of what a gun is. For the longest time it was seen as just an everyday tool. Now the media, movies, music, games, etc show them only as weapons to be used against other people. That change in perspective and the narrative around them cant be a positive. Just look at this board and your interactions here. You, relatively anti gun, see it as a weapon. The people who are around guns everyday see it as a tool. Which is why the hammer comparison keeps coming up.
Culture in general. We dont fix problems, we ignore them. Until they blow up in our face. We wont even take action to head it off. The slighest inconvenience isnt allowed, it's a wrong worse than taking away a Right. We feed off of crisis as a society. So instead of addressing items that lead up to violent actions, that might inconvenience all of society, we want to take guns away. Ignoring the problem.