yknow smth i didnt consider is multiversal travel
if there are infinite universes there are infinite versions of all the teams(eg; infinite versions of teams morshu, wheatley, darwin, earth, mojo jojo, shadow, etc)
if multiversal travel methods exist(and i wouldnt say they dont because again, infinite universes = infinite possibilities), then one of these alternate teams could accidentally stumble upon the main tmcu(like for example team earth #857 warps to tmcu #749 thinking they were going to tmcu #001[your tmcu] and then get stuck there)
just a thought