Typically it’s that they play all the cards on their turn as quickly as possible and then you’re stuck watching the queued up animations after the rope ends there turn so they’re not cheating. In this weeks brawl with a bad draw I managed to do 17 damage turn 1 and draw 3/4 of my deck. Would have been an OTK but my apm was too slow.
That been said, recently people have been caught hacking the servers to remove the animations. Started with wild and has spread to BGs. Hopefully this minute group of people are caught and banned. So it’s 99% likely they weren’t cheating and just got an unfortunate side effect of new stuff being added which queues up extra long animations, which will hopefully get patched. In the 1% where they are actually cheating, hopefully they get caught.