Probably for the same reasons Texas and Florida have so many mass shootings despite having the lax gun laws that the NRA said would stop mass shootings. Because crazy people don't care about gun laws one way or the other.
California, Texas and Florida have so many mass shootings, because they are the three most populous states. Between the three states, they have about a little more than a quarter of the country's population (about 27% per 2018 stats).
I agree totally. Mass shootings went down for a while because the media (and politicians) weren't crowing about them as loudly. Then after Sandy Hook, they did, and the rate of mass shootings went up.
Laziness, apathy, lack of self discipline, low self esteem, pathetically poor parenting, "my country owes me" attitude and ignorance. Mandatory vasectomies and tubes tied.