Who, of the horde of candidates is not on the ballot in all 50 states?
And why are they still being allowed to be muck up the debates?
As to why they are allowed to muck up the debates, I think that is not really a conspiracy, but there is some string pulling to attempt to condition the public to believe that birth abroad is no big deal. Katayl/Clement, nearly all the "simple" articles, the uniformity of misleading by politicians, press, etc. Cruz had to know that a flim-flam was going to be perpetrated. He's just the point man.
I think the PTB resist putting eligibility checks on the states, because that makes it harder to perpetrate the flim-flam.