Silly rabbit tricks are for kids. The park is less than a block and a half in size with another sliver of land about a quarter wide running another couple blocks. You could never get twenty five thousand people in such a small area. It would be packed body to body and totally have shut down and gridlocked the entire area, which pictures and headlines would have clearly shown but that simply isn't the case. The stats come from a private security company hired for the event...being also located right across from the country's largest low income subsidized apartments they probably counted many people two, three times coming and going from the secure area back and forth from home. I've see what over twenty thousand people look like stretched out and this isn't it. Now he may have outpaced his democratic counterparts but he has a long, long way to go to meet Trumps fifty three thousand that showed up at just one event recently.
As far as the video this was staged. A deliberate attempt to try and sway younger non white voters that Sanders politically holds the best chance at them seeing the radical left agenda's implemented.