I'm going to disagree that MC caused their relationship to falter. It was already broken before he came along. Josy started crushing on MC early in the summer, not long after she got in her relationship with Maya. When MC got to B&R the girls had not communicated for some time. Josy was considering moving somewhere far away, which doesn't bode well for keeping a relationship with her partner who is off at college. Each one of them fell for him without the other around, so they weren't that committed to each other. Their original relationship was based on stolen moments, where the thrill of romantic escapes overshadowed their fundamental differences. When that was taken away they didn't really connect anymore and they started looking elsewhere. Josy zeroed in on MC, and Maya was astonished to find she could be attracted to a guy but fell for him anyway.
When M&J are together all the time they don't mesh well other than having sex. If they don't have some kind of conflict to overcome they just don't get along that well (think about them buying costumes or Josy deciding to move in at the HOTs house). MC has to set up a special date for them in his room with all their favorite items and a romantic atmosphere to get them to talk some of their issues out, something they wouldn't do on their own. When not in the throuple (or whatever it is now) both girls flirt with MC and even come out and directly say that they would be good with him alone. If he's not in their relationship they are going to break up, and MC will have the opportunity to hook back up with one of them. For Maya and Josy MC is the glue that holds them together.
Here you are wrong. They didn't talk to each other until the MC was with Josy in EP2 and Pete took her cell phone away from Josy. So they haven't spoken to each other for about a week. Because Maya didn't know that Pete had taken Josy's phone, Maya thought that Josy was ghosting her. But it was only a week and Maya got angrier and angrier. At the beginning of EP4 they clarify this. Not talking for a week doesn't shake up a relationship so much and Josy also had a good explanation for Maya.
Yes, Josy told the MC so she wanted to go far away. But where did Josy want to go? We find out about this from Maya in EP3, before Josy shows up. Maya said that she thought that they would break up because they haven't seen each other in months and haven't spoken to each other in a week. Her plan was actually for Josy to get close to B&R and for them to meet secretly. This all happened through the MC because Josy and the MC worked together. It was the MC’s fault.
They do not fit together? In EP6, Josy and Maya have a movie night together with Mona and Camila. In EP10 we see old pictures of Josy and Maya. They looked happy. In EP8 they talk together several times.
Instead of always seeing the negative, you can also look for the positive. But okay, if you don't want to have a three-way relationship, you shouldn't.
When you and Jill discuss pictures of you naked with your cock over the campus, she says that people don't recognize MC easy because of the mask, and Jill hints that she recognized him by his dick. 
