The article you posted states that the death prediction you claim was based on if citizens made zero lifestyle changes in response to the pandemic.
"in an UNMITIGATED epidemic, we would predict approximately 510,000 deaths in GBand 2.2 million in the US"
Things like the shutdown, self isolating, social distancing, and mask wearing are all mitigating factors that drastically reduced the severity of the pandemic. If anything, it looks like they underestimated since we've still had so many deaths and other negative outcomes despite hundreds of millions of people making major lifestyle changes to try to slow the spread.
I agree that gathering for the protests was extremely hypocritical and, though most protesters wore masks, many didn't and contributed to the spread of the virus. That said, you should look into how many choirs had many of their members catch the virus. Singing projects tiny water droplets containing the virus much farther than talking does (though shouting at the protests would be similar - and I saw many clips of that happening in close proximity to others). Blocking those droplets is why wearing masks does so much to protect people from getting sick.
I hope you can understand how many factors of the pandemic you are not considering when you make claims that downplay its significance. The pandemic can be defeated, but people have to be on the same page and understand how to fight it if they want to make much progress. Life could get closer to normal more quickly with less damage to the economy if people wore masks in public areas, particularly indoor areas.