Bush had the Westroads Mall Shooting in Nebraska, Nick Sheley’s rampage in Missouri and Illinois, the Virginia Polytech shootings, and a couple of others. Wackos are going to run amuck regardless of who is in the White House.
In terms of the definition (four murders in one event equate to mass shooting by FBI standards)....there’s been a trend going on for roughly forty years. Prior to the 1970s...you could probably halve the statistical average. This is why they are always so careful about telling the story. I’m also suspecting that some reporting prior to the 1970s simply didn’t get reported into any national numbers (what happened local....stayed local). The internet has changed that and made people think they are part of some national trend.
For the last five years....if you dive down into almost every single mass shooting, there’s some type of drug situation involved. Even if the cops note drugs....it’s only because they didn’t test the subject or really do indepth analysis. I suspect if do a twenty-year search of records....most all of the mass shootings will show some drugs in the shooter.