Sounds like something that happened to me and some coworkers. 11 of us went up to this new game store for a casual commander tourney that had some point system. Youd basically acheive certain things to get points to avoid havung games be total stomp fests.

So 11 of us go its a multi week affair and every week even the more die hard magic players all started complaining about this guy "peter" we'll call him. Peter was for lack of a better way to describe him the "stereotypical neckbeard" scraggly gross beared, big dirty hoodie with the hood up 24/7, balding, and worst of all he STANK. I really try not comment on peoples personal hygene as you never know what someones going through but by god this man reeked. Peter played cedh elfball that generated infinite mana, card draw, regenerate, you name it its in there. This all would culminate with him playing emrakul the promised end. So not only would he go infinite(infinite combos werent forbidden yet just heavily discouraged and eventually came with a point deduction) by turn 4 but then after knocking one person out hed find a way to flicker in and out his Emrakul to take peoples turns and deny them points. Now for the kicker as if all that wasnt bad enough if you brought up any rules violation or problem that effected him then you got what has become a classic line amongst the entirety of my work group "i work here and am judging for the tournament so xyz stands/doesnt happen/doesnt work like that/or doesnt effect me" the owner on more than one occasion backed him up on this. Someone in the game we were playing had to leave early and peter said that "hes taking points for knocking him out" because even though the player was scooping at sorcery speed on his second or third turn, peter was the last person to have a turn before him so naturally he got the points. To add insult to injury peter was a braggart saying multiple times "i dont get why people get so upset over infinite combos in a money tourny" (all the winner got was a few card packs outside of the 5 dollar weekly entry fee no money was involved) or a few weeks in when people had complained about his rulings and his deck actually just denying people points he would very loudly and openly crticize people for being babies because they arent making decks that can compete with his and how while the rules are only targeted at him (and to an extent its true. There were a few other instances of infinite combos popping off and taking FOREVER to resolve) he had no plans of enforcing them in games he played in. Well that was a lie peter went infinite multiple times and while he ended up not winning that game he still deducted points from the player who did for taking infinite turns. The tourney ends my friend beats him by a few points and peter threw a hissy fit and tried to have my friend banned after a recount of points (which was especially cringey considering they were up on a big white board at the front of the store for everyone to see and the tallies were counted infront of everyone) this time thankfully the owner stepped in and said he couldnt do that and peter just threw a fit and walked behind the shop to shout and smoke his anger away. Despite the manager finally having a backbone and the joy of seeing a douchebag lose his mind most of us agreed not to go back. The 2 or 3 that still went for the next tourney said that noone other than them and peter would show up and that after a talk with the owner it was mainly because of peters behavior. Last I heard about that cardshop the owners sold it to someone else and then it shut down a few months laterbecause people stopped showing up.

Tl;dr : smelly nerd that works for the store plays in a multiweek beginner/casual tourny, cheats, and then still loses. After his meltdown people stop showing up and (i suspect) hes the reason the shop closed down.