For what its worth, NYC had large protests through all of June and saw no spike. Mask usage was also high through them + regular use of hand sanitizer (handed out by organizers in some cases). It would appear that spikes are a function of either indoor activity or large crowds without masks.
Deaths have declined for various reasons, including improved treatment (rolling patients and avoiding ventilators). Also we have not had the overwhelming of hospitals that took place in NYC and Italy repeat yet. Between the protests and people cutting loose over the holidays, I certainly hope we don’t see a repeat of that.