first of all, cheating discussions aren't allowed in forums, especially mentioning usernames
if you suspect that someone is cheating, then simply report them and the staff will take appropriate actions
however, here's my personal opinion: thinking logically, the person is most likely not cheating. Anyone who ultimately reached legend league had this moment of "spark" in which they were motivated to play chess a lot. He (or she) is just one of those. Also, the player was playing blitz and not rapid. It takes hours and dedication to play such amount of blitz games per day, but it's still possible. You say it's very unlikely, but you're confusing it up with the idea that a single member in your division among all of you is putting efforts. it can be anyone, and in fact, there are many divisions where you see people like that
anyways, if you suspect any player, just report it
Dear Chess.com
I am writing an email to you with regards to a player who I believe is cheating due to the unlikelihood of their situation.
I am Purplegenix, and I have been playing Chess for a very long time. You can see that I have had an increase in activity recently. I played the game today only to see that a player who goes by deleted has been leading the Crystal division with 1026 trophies, but what brings up suspicion is the fact that they are ahead of second place by 803 trophies, and that is a huge increase. The margin is approximately a 360% increase. Although this is humanly possible, that is not the main piece of evidence I have; I found that they have played 188 games in the past 7 days, which is or 27 games a day. Possible? Yes, Likely? No, I also found that they play 334 games in 30 days. Now this is all possible, yet it is not very likely, so if Player8083 is not cheating, they are probably smurfing, as how is it possible that an account made a year ago with such statistics is only in the Crystal League?
I find this entire case extremely aggravating, and I implore you as a business to either fix your matchmaking or terminate this account.
Sincerely Purplegenix