They're probably just professional agitators rather that protesting about anything in particular. However, if I was part of the protest, I would be protesting that 8,000 mainly unmasked people can go to a football match and hug and shout (plenty of pictures available) whereas only 30 people can attend a funeral service and have to sit six feet apart (also plenty of pictures available).
More than that police chiefs were negligent in that they allowed the event to be policed by officers with no riot gear. They did this, it seems, as they did not want them to appear "confrontational." That seemed to work well.