Did the 1 not get taken down because they didn't believe the 4 would have won?

I don't understand how an unquestionable foul in the stretch is permissible.

The only reason I can think is that they are ruling that the 1 would have won anyway. But on that basis, what stops superior horses from just mugging inferior horses? Isn't this a major safety issue? If you are the better horse, it is okay to take out the inferior horses on the way to the wire? But if you are an inferior horse and you need to take out an opponent, then that is not okay?

What am I missing here?

Also, when a horse checks severely, how can you say what would have happened if the horse wasn't checked severely? That seems like something not even Karnak the Magnificent could divine.

Sometimes I just dont understand this sport.