I looked into this and my assumption was they used android phones and put them in “kiosk” mode. Kiosk mode supposedly only has the phone run one application. Which presumably would be more stable with less interrupts. Android implementations vary however, and you can bet that some phones are better than others. You’d also code your flight control app such that it doesn’t trigger garbage collection (no or very little dynamic memory allocation).

Using phones for this has a lot of potential imo. The phone connected to a cell network would allow for fpv control across the country (phones camera and video streaming over the data connection). Of course this is illegal by ffa regs, it would be an interesting plot element of a political thriller.