Why did Jesus suffer for sinners and not victims

[John 6IX Breezy]

But is it? Fertilization has causes. The egg would not have been fertilized were it not for "the couple had intercourse," or some other cause that is necessary for fertilization to happen in the first place. That's the point. You're choosing the middle domino as the "beginning of a new organism," ... but what I'm saying is that there are many dominos before that (and after that) that are necessary for a human birth. Why not assign equal weight to those?

I understand what you are saying, but the middle domino (fertilization) is the beginning of a new organism. (This classification is not arbitrary; I've referenced to an embryology textbook before which you may have missed it.) The preceding dominos might be of relevance to fields such as evolutionary biology, which take an interest in sexual selection; and the succeeding dominos to fields such as psychology. But fertilization is of interest to embryology and obstetrics. Here's an excerpt: 

"Fertilization [emphasis added] is... a process of carefully orchestrated and coordinated events including the contact and fusion of gametes, the fusion of nuclei, and the activation of development. It is a process whereby two cells, each at the verge of death, unite to create a new organism [emphasis added] that will have numerous cell types and organs. It is just the beginning of a series of cell-cell interactions that characterize animal development" (p. 248).

Reference: Gilbert, S.F., Barresi, M. (2016). Developmental biology (11th ed.). Sinauer Associates: Sunderland, Massachusetts.

There are single-celled organisms that bypass this process. And (hypothetically) you could do the same with humans.

Right; the embryological definition is exclusive to sexual reproduction (and multicellular organisms like ourselves). I'm not entirely sure I understood your hypothetical (perhaps due to my ignorance of totipotent cells). I would most likely import information from asexual reproduction, or the embryology of twins, into my answer. But even if your hypothetical requires an entirely novel approach, I would consider it an exception to the rule (much like asexual reproduction). In other words, it would be in a class of its own, and would not affect our current definitions.