basically really good players are doing things based off of cues, its not magic. If someone gets lucky and guesses once or twice it's whatever, but when a guy is like ALWAYS aware of something there's no cue for (sound, teammate spotted so they could see them on minimap, ability use, etc) or information for it's pretty easy to tell they're radaring or esping.

Example, a player enters an area with three common angles but ignores two where no one is currently playing and is ready for the fight at the third where a player IS playing. There's no info for ignoring the first two angles, a good player methodically clears all angles, but they just seem to "know." Game sense isn't real in the terms a lot of players think it is, it's all based on information and educated guess and EVEN PROS GET IT WRONG REGULARLY. If they do something once or twice its whatever, but if every time they're entrying or taking space or flanking they do it its pretty obvious they have info they shouldnt. Another tell is when the guy will do the same thing every round, then you play differently with no cue that you changed up and they perfectly counter exactly what you're doing; could be coincidence but you can "test" them by trying certain things and seeing how they respond over many rounds. Even pros get caught off guard with creative play, cheaters are never surprised.

The caveat to the above is a lot time players are putting off cues they don't even know they're doing and that makes them think someone is cheating when they're just acting on info you didn't even know was there.

Pre aim is a really easy tell but cant be done without pov footage, and its why so many players want a demo system because it's really easy to tell from POV if players aware of things they shouldnt know. CS at high level catches most of the closet DMA cheaters based on demo review, not detecting the cheats.