Since Trump knows of the risk his rallies pose and goes ahead with them anyway there is a taste of negligent homicide.
Since the result of a rally is an uptick of some 20% of new cases leading to a number of deaths there is a sense of the number of deaths resulting from his intentionalnegligence.
Some reasons you know why they don't get the mask thing: They are distrustful of experts and authority. They see themselves as rebels against government, and as independent thinkers. They don't care about the dangers they may be placing others into. Those and other reasons all bottled up in their being captured by Trump.
It was Plato who said, “He, O men, is the wisest, who like Socrates, knows that his wisdom is in truth worth nothing”