It is a certainty that larger vehicles are more likely to cause pedestrian injury and fatality, all else equal. This has approximately nothing to do with "climate change activism" - for example, nothing changes in terms of pedestrian safety if the huge SUV or truck in question is hybrid or electric, except perhaps becoming even more dangerous because it's quieter.

Above all else, speed* and bad road design kill pedestrians. Speeding is ubiquitous in North America, and roads/streets are absolutely terribly designed, with an almost singular focus to facilitate speeding and reduce cognitive load on drivers.

* - though if we exchange 'momentum' for 'speed' we can tie it back to the size/weight issue.