https://www.statista.com/statistics/1384790/motivations-of-mass-shooters-us/

https://www.latimes.com/world-nation/story/2019-08-07/what-role-does-ideology-play-in-mass-shootings

Here are just two sources from a preliminary search.

You are correct the extreme vast majority like in the 94th percentile are white males that commit mass shootings.

I was able to find that a lot of them have links to extremism specifically right wing extremism but ultimately almost all of them again in the 90th percentile were suicidal in a state of crisis and had some sort of mental illness coupled with all of that.

The actual primary reason why they shootings happen is due to mental illness almost exclusively.

There’s definitely some correlation between right-wing extremism and even more specifically magas but not enough to exclusively blame the shootings on that.

Supplementary, I did find one or two not very good sources that indicate there have been an uptick of mass shootings specifically due to Donald Trump’s re-election. But like I said these were not good sources.