I don't get that at all, I get that Mike and Jay have known each other since the 90s/early 00s, and everyone else came along later. I'm sure there's some nerd lore on Reddit or something, but I'm pretty sure Mike and Jay knew each other before they knew anyone else in the group.
I admit I could be wrong, but from their documentary "How Not to Make a Movie":
Mike: "Rich Evans was involved in my short films since probably mid-high school."
Rich: "We'd come up with crazy, stupid ideas. Things we'd never possibly film cause we didn't have the resources. Then we'd go to his house after school and try anyway."
Mike: "I'd put Rich in costumes in my parents' basement and then throw things at him. And uh, make him embarrass himself for my own amusement. (laughs)"
See also:
IIRC Mike met Jay through various indie Wisconsin film fests when they were in college. Mike had some "pre-RLM" "brand" (for lack of a better term) which had some collaborations with Jay, but Jay also had his own "brand" he was making things under -- mostly really sick, gross-out, John Waters-type short films, which actually got some decent reviews in local papers (I remember, because I remember trying to see how I could watch Jay's early stuff and only found the reviews.) In fact I think right before they joined and created RLM, Mike and Jay had some kind of a falling out. (Looking further into it left me with a grimy feeling so I stopped.)
Everyone else came onto RLM wayyyy later, probably post-Episode 1 review.