Who goes to the lower degrees of the CK? To put it bluntly, there is no plausible theory that makes sense or is politically correct. We just don’t know, and I defy anyone to even imagine a scenario where someone is worthy to enter the “Celestial Kingdom” but isn’t worthy of the highest exaltation.
My theory is that Joseph Smith revealed the 3 degrees of the CK to sort out the true believers and the super-duper true believers. He already had a bunch of people who were pretty much assured of getting to the CK based on the 1832 revelation (D&C 76), but if that was the case, why would they care about celestial marriage and/or plural marriage? The only way to make it work would be to reveal to people that even though they will be in the CK, they could end up in coach seating while others are flying first class.
There was also a time in the Church where people who didn’t get married in this life were assumed to not get married in the afterlife; this Earth was their only shot. But now we are in the era of “happy feelings” where we can make anything up that we want to if it makes us feel good, so now we teach that even if someone lives in Provo, Utah their whole life and is surrounded by thousands upon thousands of single Mormons, and they have access to the internet and LDS Singles, it’s still not their fault if they don’t get married, so God will sort it out in the end.
So at the time of section 131 (1843), I imagine the answer to your question would be this:
CK – First Class Seating – Polygamous Marriages
CK – Business Class – Monogamous Marriages
CK – Coach – Single people (ministering angels)
But we really don’t know. The answer to your question probably died in the summer of 1844, and is buried overlooking the Mississippi river