Trump takes credit for every positive thing that has happened during his presidency, including those he has nothing to do with, so why shouldn't he shoulder the blame when his MAGA followers start killing people, which IS his fault?
As to why these horrible events happen, it's because the NRA WANTS them to happen. They want everybody cowering in fear and packing heat. And as far as the motivations for those acts are concerned--we decent people were shocked when we heard that dozens of Hispanics were shot in El Paso, but lets not forget that millions of Trumpers came in their pants when they heard the same news.