Organizers did good job to hold any unwanted people out - there was a bunch of guys with dirt bikes who scanned the areas day and night and lot of surveillance personell and equipment (helis and drones) from police and border guard.
Organisers have indicated that they found some people that were ignoring those restrictions but they all were escorted out of the area with no bigger incidents. Those scattered groups of people that were visible from the live feed was most likely locals who live around the stages and their visitors or accredited media personnel. Afaik every local inside the perimeter was contacted and they had an opportunity to register some friends and family members who got access to the stages while the event was running.
Edit: While scrolling Instagram I found this account of one of the bike guys. You can get a glimpse of the job they did + one good video about a disguised camper van that they found: https://www.instagram.com/stories/hi...1128886782326/