This timeline reveals how the “deranged man” hypothesis leads to faulty explanations based on individualization and protects white social movements from the scrutiny that non-white movements receive. The ideological context of this has been studied extensively by journalist David Neiwert.
This list is quite long and definitely establishes a pattern of political violence. But if every incident is treated as an individual act, taken in isolation, and explained by reference to individual characteristics of the perpetrator, then, the social, political and cultural background disappears, leaving the emerging social movement unexplained and unaccountable.
It is a common phenomenon, long studied and explained by social psychology that when individuals from our in-group or privileged individuals commit questionable acts, these acts are explained individually. When individuals from out-groups, or groups that are socially unpopular, commit questionable acts, these acts are explained as part of group membership, as categorical. The former are exceptions, the latter are representative. That is how racial and ethnic prejudice persist and how white privilege is preserved. One only has to imagine what media discourse would be, had the shooter been non-White, Latino or Muslim.
So, this timeline is one of white, domestic terrorism, fueled by seditious rhetoric from various media outlets and figures. The fact that the perpetrators are not part of a single organization does not change that fact. Social movements can exist without social movement organizations.
As for mental illness, it is the easy individual culprit, the one factor that, without further elaboration, explains everything. This is as if mental illness existed in a social and cultural vacuum, which it does not, of course. To invoke mental illness may explain outrageous behavior (i.e. behavior outside of the norms) but it does not explain the commission of specific acts (assassination attempt against a Democratic Congresswoman, that still remains to be explained). But to invoke mental illness provides some relief that we are not dealing with organized violence and that therefore, there is nothing socially and politically significant going on and no deep questioning to be had.