By now, we ought to be seeing some evidence of increasing Covid-19 cases from the mass protests. The fact we are not raises very serious doubts about the coronavirus lockdowns and other non-pharmaceutical interventions, many of which are still ongoing.
One explanatory hypothesis is the weather – that outdoor protests in warmish weather might have decreased the infectious potential of Sars-CoV-2. This seems highly unlikely. Even if there is such an effect, it almost definitely doesn't outweigh the close proximity of protesters to one another. Another explanatory hypothesis is that most protesters are relatively young, and therefore unlikely to fall ill but may asymptomatically transmit the virus. This could well be the case, but there is not yet enough data to support this hypothesis and I am not currently convinced this is the most compelling explanation.