Hikaru talking about the cheating allegation against him: https://www.youtube.com/watch?v=Zm2R--_fBj0 I'll add that he live streamed the tournament he was accused of cheating in. If you've ever watched how fast he moves and quite often pre-moves & talks through his strategy as he goes, it'd be very surprising to see that he cheated (and I don't even know how he'd go about doing so - he's faster than the engines!).
Do I think it's possible to cheat at his level, it would be an art to cheat in rapid and not get in trouble at the rate he plays. But sure, I'll bite, why not.
You can see that Hikaru has the ability to calculate and anticipate standard play far above his opponents, he calls out their moves before they make them. He clearly calculates both, he calculates the human line for him and his opponents.
You can also see the tilt in chess vs say LoL in almost real time. You can begin to spot fatigue in an hour-long video, multi-hour stretch, you can see Hikaru get tried and change the way he plays, slow down, go for positions that are easier to play because he knows himself very well.
Hikaru taking 2900s to town on chess.com simply looks like he is playing above the field at that pace. In a real tournament, with 90+ minutes, 2500-2600s give both Magnus and Hikaru trouble because there is so much more time to calculate. I think the reason why Hikaru is so strong, pattern recognition at this speed, instinct, and time spent playing, not strength necessarily in classical chess. (e.g. he has never been world champ)