[andrekandre]

they are most likely using a controller hooked up to a bot/laptop that exploits flaws in the code with inputs at high speed (much faster than a human could) that injects code into live games

a good video that makes this tech more understandable (with explanations at the beginnimg and an amazing demo at the end) https://www.youtube.com/watch?v=PNbkv_DJ0f0

and some background https://tasvideos.org/ArbitraryCodeExecutionHowTo