This sort of thing has been done.
There's a real world geolocation based game called Ingress played on phones, occasionally there are big organised meetups ("anomalies") where hundreds / thousands of people "battle" in a real world physical location.
Can get many "anomaly" game situations where tens / hundreds of players in a relatively small area.
(In the game a player is on one of 2 teams)
One of the teams, before one of these events, set up a strategy where people would at critical points shout out the well known phone assistant commands such as "OK Google", "Hey Siri" and taht would screw up some of the opposing team from playing Ingress as teh assistant would cut in (the assistant subverting team having briefd players to disable their digital assistants to give them the edge)
This was ages ago, so the assistant "attack vector" on a large scale is not new by any means.